Mostly, it's for the rest of us and our viewing pleasure. We like to know who we are talking to, makes communication a lot easier for some of us.
That said, most of us soundly ignore the welcome section, it's not that we don't like you, we are just lazy.
So, go ahead and introduce yourself, or not, but mainly don't get worried if we ignore you. Just jump in somewhere and post something. We don't bite and the worst that will happen is that we will ignore you some more.