I think the reason why low rp events occur more is, events are just often thrown together with little planning, and it is much easier to just throw some lazy event material at a wall than it is to organise something a bit more fleshed out.
I do think Devs do to an extent impact roleplay, it's pretty rare to see roundstart roleplay due to the tedium of the squad cargo system system. I think people reflect what they see, if they see roleplay, they'll engage in RP, if they see people throwing cream pies at Co, they'll do that.
Most RP is player led, but yeah some barriers could be removed to help that.