So this is taking a shot in the dark but responding to the OP about why it may seem like there are more Minigame type servers (or the like) vs things like RP, may have to do with monetization. I am not hating on anyone, pointing fingers, or meaning to be rude but a server requires some sort of funding in order to exist. This could be through donations, sales of ingame things, purchasing of boosters, the owner paying for the entire thing out of the care of their heart, etc. Minigame servers are able to make money easier because they can sell all sorts of things ingame, while an RP server may not have such opportunities because no one wants to RP with someone who just buys everything and proceeds to show off with it.
This is just my opinion and random thinking while sitting around late at work with nothing else to do. Feel free to point out obvious flaws or provide further discussion!