Actually I think that thats because people have nothing to do. Like if server is freebuild/creative, they make what they can do best (mostly box house) then they start to run around screaming "please promote me!". If they dont get what they want, they get in their minds that this server sucks or something like that and it needs to be griefed/hacked/spammed.
If you look at my profile, You'll see my Freebuild server. I get about 30 griefers a day. All of them build a boxy house from one material (usually diamond block as they think it represent them as rich person) and then tries to grief and get banned. Any other person who spams get banned too as i have protections for that, though you cant avoid all of those People who's mind is already "effected" by today's society.
Cheers and good luck!