I think it varies person to person.

Personally, its how common it makes some pokemon feel, catching a Diagla in DPP or BDSP feels way better than PoGo.

PoGo can be a lot of fun but i find it removes some of the gravitas of finally getting to capture the box legendary or a shiny.

I mean yeah, if you are just after them for a NatDex but trying to do the game specific dexes requires the pokemon having the game specific origin tag

Also, imo, PoGo-mons just dont have the same weight(?) to me, I'd always rather a mainline game version of a given mon