Artists want 2 things, attention and/or money. A few "pros" only care about the money, a lot of "hobby artists" draw for fun and only post for attention (If they didn't want attention, they'd just keep their art to themselves. There are people like that, but they aren't posting art, so we won't worry about them.) A lot of artists are somewhere in between, posting for the fun and attention, but all for making a few bucks when they can.
Some people get overly protective of their art. In many cases, these are "hobby artists" trying to emulate what they see the "pros" doing. Its not right for someone to take your art without permission, but in a