I think it's because they get banned before they've said everything they want to say.
Some people obviously have more to say than most, they want to be heard, so they return under an alias.
As long as it's obvious who the alias really is, and the mods don't care, then it's not a big deal.
The real problems are with the scammers creeping back in all the time.
So, they come back and argue a ton more and one day go nuts again and get banned again. :grin: Then they post on their FB, they're victims of the mods here.
Then they come back again.
So, really, it's like the no child left behind program.