@ Ald - yeah, at this point I'm pretty much talking from a purely theoretical fictional standpoint. In terms of game mechanics, I well understand the reasoning for not including point defense on larger vessels and instead looking to try to force fleets to coordinate their action to provide local defense against smaller craft.
I see your point.
However you can either:
1) Devise a system that neutralizes a percentage of incoming fire through active countermeasures, such as point defenses.
or
2) Devise a system that neutralizes a percentage of incoming fire through passive countermeasures, such as a decreased susceptability to damage.
If we rightly, in my opinion, assume that EVE's ships are crammed to the brink with their equipment any noticeable addition would make it necessary to drop something to free resources. That means either lowering their efficiency in their specialized role, such as dropping a turret, or decreasing their passive defenses.
Since we have absolutely no idea how the numeric values of such a trade-off would be, we can not judge if it would be a good or a bad move.
We can, however, provide an in-world conclusion based on observations such as no navy using non-drone point defense ( actually, NPC's don't even use drones ) but employing highly specialized ships that are 100% effective until they literally disintegrate.
I don't want to sound cheesy by going "That's how it is ingame, durr", but I think you can actually wrestle some believable reasoning out of the situation.
Fair enough reasoning, and yes - if a ship could be said to loose some of its effectiveness due to the addition of another set of systems, I could see why it would be avoided, particularly in some of the less flexible hulls.
I'll make an arguement here that some limited CIWS should still be present. Here's why.
At current in real life - and yes, I know I'm throwing in a massive red herring by explicitely bringing up the "but IRL" arguement; it seems to me that something that works now should work 20,000 years in the future, though - there are two general types of point defense systems.
The first are "ship-integrated systems", which refer to systems which are linked to the ships' main fire control systems and require significant modification of the hull in order to fit a mount, ammunition hold, and any additional fire control equipment; in return, these systems have considerably greater stopping capability and are more likely to form the main portion of an antimissile shield. Examples are the US SM-2 missiles and Dutch 'Goalkeeper' system. Systems like these, I could understand the designers of ships in New Eden not wishing to add to ships at random, as they would likely reduce the abilities of some more focused designs.
The second class, however, are what I think of as "plug-and-play" systems - largely self-contained, not requiring major modifications to the hull, they can essentially be bolted onto the hull in any fortuitous location, plugged into the ship's main power supply, and allowed to operate autonomously. The downside is that they tend to have far more limited effectiveness than the first type. As has been pointed out, however, because of EVE's ships' spectacular ability to absorb damage, even a minor reduction in incoming damage - say, 5 to 10% - would be a not insignificant tactical advantage.