Because I am an interesting and friendly guy and over the many years on dA my activity has become less and less about "I wrote this, look! Look!" and more on chronicling what it means to be a writer and the experiences I've had and the lessons I've learned, all in an attempt to make sense of this passion so many people share and to, hopefully, highlight the path to greatness so we can all be better writers and better people. It's as beneficial for others as for me.
Also, I'm loud and opinionated and if it's good enough to get Fox News viewers, it's good enough for me!
As for the second part of your post - The way to be your own best salesmen, for creators is, I think, is to meet people and interact with people and to be humble and friendly. Be enticing and sell your work but be honest, too. People are just as often fans of creators as of creations.
If my artwork is good enough, it will get noticed by others. When you think about it though, usually when it comes to works that get noticed a lot, people who comment on it usually become of one mind. I mean, sometimes, you get stuff that is just like "meh, could be better" but then some people think it's great and so on and so forth. Eventually, you don't get constructive criticism or proper feedback because everyone is just going "ooohhhh that's so cool" and they don't look harder. So what's the point of it all?