Couple of reasons.
A) Samira is a type of character concept I've played in multiple iterations across multiple universes over the last decade. I endlessly refine the concept to try and smooth out mistakes, deconstructing and reconstructing it. Like most of the characters I play, she follows my style of taking a few RL traits of mine, exaggerating them, and building a character around them. In Samira's case, the traits are submissiveness, isolation, and fear. I play those traits specifically because they are something so rarely seen in RP. When most characters are badasses who don't afraid of anything, the coward who runs and hides when threatened stands out.
B) Why Amarr? Immediately before coming to EVE, the RP universe I was playing was a Forgotten Realms server on Neverwinter Nights 2. I played another version of the Samira concept there, as a Red Wizard of Thay. When I came to EVE, I found the Amarr Empire felt very similar to Thay, due to pseudo-evil slave culture with Middle Eastern aesthetics. Most specifically was the two-race hierarchy of the superior overlord race and the inferior race of spiritual tribals (Mulan/True Amarr and Rashemi/Minmatar) of which many are enslaved and others are converted into the culture and free. Ironically, in that case it was the overlords with the tattoos, and mankind was seen as greater than the gods (thus, Thay would actually be closer to the Khanid Kingdom. Hell, the pre-pact relationship between Empire and Kingdom is extremely similar to the relationship between Mulhorand and Thay...).
In general, I often get drawn to the darker, hyperpatriotic factions. In Star Wars I favor the Galactic and Sith Empires, in FR I liked Thay as mentioned, so in EVE I'm attracted to the zealous Amarr Empire and the dystopian Caldari State. On the other hand, in WoW I played draenei. This opened me up to how interesting religious RP can be, which is another reason why I find playing Amarr fascinating. I love playing strongly religious characters. In WoW I also played a human noble, so Amarr's very feudal culture also appeals to me since I've done a lot of research into that already. Basically, the Amarr Empire is many things I like in one single faction. Dark, religious, and feudal.
C) Why a slave? Over the decade I've RP'ed, I've seen a lot of slave characters. Especially in Star Wars. The vast majority of the ones I've witnessed have always been the same things: typically the "sex slave" and the violent "FREEDOM!" emancipationist ex-slave. I personally am the type of RPer who loves to
deconstruct things, taking common tropes and then applying a more realistic spin with more realistic consequences, so in this case I wanted to deconstruct the
Born into Slavery trope by focusing on the psychological damage and not the "quest for freedom". I wanted to play the slave who has been conditioned and indoctrinated and knows nothing but life as a slave, the slave who
blames herself when she gets punished because she's been brainwashed to think of herself as naturally inferior to her masters. And to explore, as many people have pointed out IC, Stockholm Syndrome. Essentially, I wanted to show just how messed up a slave-born character would be.
Without going into the sexual dynamic. I wanted Samira to be a proper "labor" slave. I made her Custodian a woman specifically to avoid any potential implications.
But there's also the more local deconstruction of the portrayal of Amarrian slavery itself. With Samira I wanted to go against the grain of the typical pro-Republic ex-slave and instead show an example of what is actually the more common kind of ex-slave: the one who is fully converted and assimilated. Samira is one of the many ex-slaves who, after release, chose to stay in the Empire and continue to believe in God and be good Amarr citizens, who have been taught to be faithful, loyal, obedient, polite, selfless, and domesticated. So in that sense, despite the psychological damage, she is a Reclaiming "success story".
Essentially, the main thing I enjoying trying to present with Samira's slavery background is this: To pro-slavery characters, she is a shining example of the good of the Reclaiming. To anti-slavery characters, she is terrifying proof of the horrors of slavery. The question then becomes: Do the positive conditioned behavioral traits outweigh the negative psychological damage? The answer in western morality will typically be no. The answer in Amarrian morality will typically be yes.
D) Conflict. My main rule on creating characters is that they must have conflict, both internally and externally. This forces character development as it gives the character something to act against. There is no story if there is no conflict.
Thus, Samira has been built with many. For example, she's not perfectly religious. She is excellent at sounding faithful, typically one of the most fanatical speakers on the topic on IGS, but struggles to
really believe what she preaches (in WoD terms, she has faith, but not True Faith). I also wanted the conflict present in being dual-culture. She's not one of those Amarrian Matari that completely and utterly shun everything Minmatar. Samira might often
say she does, but deep down she respects a lot of Matari culture and spirituality and tries to incorporate it into her Amarrian world view, which creates conflict (her tattoos being a recent one). Third and most important is the character's indoctrination itself. It forces her to have to constantly struggle to learn how to be independent, struggle to face her fears, struggle to stand up for herself. None of these come easy, and so it makes everything she does, particularly her interactions with other characters, a challenge. This is fun to play.
E) How all of the above suddenly comes into sharp relief once the issue of being a capsuleer gets thrown into the mix.
So yeah, that's why.
To elaborate, one example I often give when talking about some of Halete's dynamics comes from the concept of 'The Beast' in Vampire The Masquerade.
Heh. Speaking of Vampire the Masquerade. I've often said that I view playing an Amarrian like following a
Path of Enlightenment. The Empire's morals and ethics are completely different from the path of normal "humanity". An Amarr will not be affected by appeals to standard human morality, because they do not follow standard human morality. They have Conviction instead of Conscience. Which is why most attempts at convincing Samira that the Empire is evil fail, because they are going by the sin hierarchy of the "Path of Humanity" while Samira follows the sin hierarchy of the the Amarrian Path of Enlightenment, which is completely different! To convince Samira that the Empire is evil, one has to break her Conviction, instead of trying to appeal to her Conscience. This is easier said than done.
That's why playing Amarr is so fun. Non-western moralities are much more interesting!