You are projecting, and pretty unfairly imo.
It’s as valid a question as any other asked ok this site, the OP isn’t responsible for other people’s rudeness in prior threads.
I’ve been here a very long time and have seen a couple of the goady types, but this post actually generated a lot of interesting reasons and routes to the site.
OK, I apologise if I unfairly labelled/accused this OP. To be fair, the actual OP itself made it clear that the question wasn't meant to be goady, but the title is a great example of how you need to understand the lack of body language in the written word and make sure that it doesn't potentially come across as aggressive. "Why are you here?" may well be intended to mean "What first brought you here?" but can equally (if not more so, subjectively) be interpreted as "Why are you somewhere you have no right/reason to be?" You have to be very careful not to instantly rub people up the wrong way with what can appear to be a goady/accusatory title.
Also, I'm assuming OP is quite new and might not realise that there are other topics, but the very nature of AIBU is to ask sometimes very divisive and/or reactionary questions. Had she posted "What first brought you to MN - especially if you don't have kids?" in Chat, it would have been clearly a friendly query, as OP intended, and not, from the title at least, easily interpreted as a demand to justify your use of a general public discussion board that has long outgrown merely matters of parenting.
Either way, whether goady or not (and I'd say the endless threads on it that we have are 50/50 at best - probably more towards the accusatory end), here's where an algorithm (if it were possible) might be useful - opposite to the one for the zombie threads. Whereas with the latter, you get the message "This hasn't been posted to in over a year, why not start a new thread?", for the very, very common questions that come up time and time again, an auto message saying "This us a very frequently-asked question - why not do an advanced search to see how it's already been answered?" could be helpful. That way, as well as avoiding annoyance, newbies would see lots more of the responses in one thread rather than spread across a hundred threads.