Super Mario Boards

I hate those games that give you an ultra-bland default theme and in order to make the game menus actually look decent you gotta pay up.

Those are also the worst too. It's manipulation too, as well, to try to make something barebones to make microtransactions more appealing. I'm not even aware of game *interface* also having mictrotransactions (aside from the dubious 3DS themes which are handled like shit), it's usually neat costumes.

I remember when getting minor stuff that barely affects anything was free

It's all about social status and peer pressure. Tying rarities to items makes players want to get the rarest items and show off, which at times will cause them to use microtransactions to get them.