They aren't as centrally and hierarchical organized as the RCC. Even most other Christian sects aren't organized like that. So this unique feature makes it distinctive.
That, and the fact that it's much nicer to poke fun at "higher ups" than at peers. So if you make your whole organization about "higher ups" there's a lot of fun to be poked, I guess.
State churches like Anglican church might be more apt comparison. And those often do look like corporations when squinting, with lot of state funding or even taxation instead of sales... You even get various managerial classes, which do need to perform slightly different corporate rituals.
