In the case of both the Matari and the Caldari you're looking at people who were forcibly evicted from their homes. Is that really so significant?
In short, yes.
You don't have to go too far to find analogues in the real world, Saede. In fact, you don't have to leave America. Despite America being the longed for new home for millions of refugees almost ALL of them retain cultural ties to their original homeland. This remains the case whether you're looking at the Miami Cubans who are separated by, at most, three generations or the New York Irish who are often separated by centuries. The Pennsylvanian Dutch. The Poles. The Italians. The Louisiana Cajuns who still think of France despite having been relocated from France to Acadia and THEN to America.
Both societies in question are defined by having to rebuild their societies after having their home culture ripped from them by a much more powerful enemy. There are differences, of course, the Matari have reclaimed their homes and original colonies - but face the terror that their home is now strange to them - so many stories, memories, languages stolen from them. Everything they can remember hints at the things they've forgotten.
The Caldari have the opposite problem, never actually beaten, they retained their culture - aggressively so - and it was used as the social glue that bound them together when they could have flown apart. To them, every oft-told story and long-held custom harks back to a place that is fiercely remembered, even though few living have actually walked the snows there. And you're right, even if the planet had been blown to smoking atoms it would have remained a rallying cry forever.
In a way the physical planet is far less important than the Ur-Caldari that is held as a symbol by the State. Even if the Federation completed the terraforming and transformed the planet into a paradise, most of the stories about Caldari Prime would speak of harsh winds, scarce resources and the bleakest winters you can imagine. In a way, kicking the Caldari off that rock means that they took THAT Caldari Prime to the stars with them, seeding hundreds of planets with Kresh trees and tea.
Is that it, though? Are both cultures doomed to eternally live in this cultural cul-de-sac, longing for things that they barely remember? Well, no, that's not true. Both races have faced no real new threats for all the time that they've been driven by these desires. The Matari still have beef with the Amarr and the Gallente are always up for twirling a moustache at the Caldari - and both these enmities continue on unabated.
It's entirely possible that politicians in all four empires could be artificially keeping the drums of war beating solely as a means to focus the attention of their people on an external threat. Maybe the Drifters will break that pattern? I'm pretty sure that Britons had a generally positive image of Germans - up until World War I rewrote that narrative. And we know that World War II could really have been dubbed "World War One: Part Two - Unfinished Business".
Of course, the narrative for our four Empires is governed by CCP. If they fail to come up with new stories, you'll see Nationalists grasping at the same old straws. And why not? That's what they do in the real world!