I think the reason why people are so blunt on here (and most forums) is because it requires less effort in doing so. It is a lot easier to say "<insert name here> sucks" or "<insert name here> rules" than it is to put together reasoned arguments. Also, short sharp jabs usually get more attention than well thought out responses and that is the reason why a lot of people post in the first place - to get attention, good or bad.
That's true that you're more likely to get a response if you post something more dramatic and less thought-out. The large gap is even more obvious if you've put in a bigger effort, then watching the people with two word answers or predictable answers get all the attention.
It is a message board after all, and maybe back in the days when they first existed, it was hoped that they would become discussion forums, so it's natural that you'd want to have replies to what you're posting. Of course that doesn't equate to which posts are better, and some people will say that yeah, there are plenty of people that read what you're posting, but I don't know it and I may as well write it to myself.