D&D 5E (2024) Spell Resistant Feat is what Spell Resistance ought to be.

[Vrindlevine]

I'm confused by this feat. Can anyone explain it to me? Why it is limited in use (beyond balance). What does its limited use represent/modal in the game world? What does it mean when a character "uses" the feat? What is the character doing at that moment?

Seems like the idea is that the character has just picked up some magic resistance, perhaps due to repeated exposure to spells (like you would gain resistance to a poison), or maybe due to some Drow/Dwarven heritage, though maybe those races don't get magic resist anymore.

I'm scratching my head a bit at explaining why its only useable a handful of times per Rest instead of always active, you would think a learned resistance would just be "on" but +1d6 to saving throws vs spells sounds rather overpowered, so maybe just +1 all the time would be more realistic?