Just recently a post of mine got deleted for no apparent reason (wasn't breaking rules) and so I posted it again, thinking perhaps the forum bugged out or such. And then my account got suspended. The entire time, there was no warning, no reason, nothing--Just me to speculate and be on wild guesses.
So even if I was breaking rules, it'd be reasonable to suggest to warn people, let them know what they're doing wrong. People don't learn if you just punish them randomly and give no explanation. So it's only reasonable to warn people so they know what's going on and what they're doing incorrectly.
Cheers.