why do you get relic upgrade materials from crystal tower?

[Absurdity]

It is tied to Bozja though as you can't start the new relic quest unless you've completed the previous Bozja quests which means getting to level 10 in there and doing the Castrum.

Which is what I really don't get. Why even give people an alternative way to farm their relics outside Bozja when you're forcing them to basically complete the thing anyway? Might as well scrap the CT grind and increase the drop chance inside Eureka 2.0

[Seraphor]

Which is what I really don't get. Why even give people an alternative way to farm their relics outside Bozja when you're forcing them to basically complete the thing anyway? Might as well scrap the CT grind and increase the drop chance inside Eureka 2.0

I think the intention was always that people would complete the Bozja content anyway, and then the grind for subsequent weapons could be done either way.
They haven't been very consistent or effective in the implementation of that though.