It quite possibly is due to some of the laws in said regions preventing it. One example would be the EU signing that big anti-lootbox law into legislation. Also while this is hearsay, I've heard gambling laws in the EU are quite a bit stricter than anywhere else.
I have no life and could try looking up local laws for your regions to see if it's more of a case that Sega can't legally release PSO2 there (without greasing some palms at least, because yay, lobbying, woo.) and is something to yell at your government about.
edit: I mean come on, look at the bugs, garbled translated text that makes no sense sometimes (or "gods be, operative") and more means Sega has no qualms about getting the game out everywhere it can as quickly as possible. What self-respecting faceless corporation turns away money anyways?