Personally, when I first got here I didn't get a user name, I wanted to get a feel for the site. See if it was for me and if I could find some help from it. Nevertheless, I ALWAYS signed my name (julie, wife to Mark 24 w/CF) under the postings.
Once I joined, I would occasionally change computers or post from work and not realize I wasn't logged in. But if I caught it, I did one of those "that was me-woops" posts.
I think it really is relevant that people care and want to know why. It has become a rampant problem of anonymous posting and not leaving a name or anything. It's not like if you get a user name we can find out who you are, your DOB, your SSN, your bank account, your address... And I can't speak for others, but it's the rude anon. postings that really get under my skin. Not the ones where someone who's anon. asks a question, but where someone who is anon. gets all snotty and hoity toity. I mean, if you are going to get that way, DIGNIFY your feelings and posting with a name.
If you don't care about the question, that's fine, you are entitled to your opinion. But clearly the person who posted the question does care and/or is curious, so if you can't answer their question at all in your post, you ought to save the rest of us the time of sifting through your crap so we can read the other responses where people do care enough to answer the question.