Why aren't there any cross-generational evolutions anymore? What I mean is things like:

Zubat/Golbat - introduced in Gen I
Crobat - Gen II

Magmar - Gen I
Magmortar - Gen IV

Eevee - Gen I
Sylveon - Gen VII
but honestly, I don't think Eevee should count for this since GF seems to be milking Eevee for its merchandise (Eevee and its evolutions get a *significant* amount of merch compared to every other Pokemon (besides Pikachu). There even used to be a yearly promotion at Japan Pokemon Centers dedicated to them. Tons and tons of plushies, cards, figurines, clothes, etc.).

We had a few in Gen II, none in Gen II, a shit ton in Gen IV, none in Gen V, and just one in Gen VI (that doesn't count). Gen VII is looking like it won't have any. So basically the last time we got evolutions was in Gev IV, something like 10 years ago.

Why isn't Game Freak doing this anymore?