It could well be that they felt they could open up to me because I chose not to have children. Other parents would likely not be sympathetic and may even make comments or just look horrified or whatever.
Well, I chose not to have a child until I was almost 41, have a wide circle of friends and acquaintances in a lot of different countries, am from a large family and married into a huge one (DH is the youngest of 7, MIL is one of 13) and that is not my experience, that I was a safe person in whom to confide mass regrets about having criminal and drug addict children.
For example the recent posts about not encountering people with families who have troubles - drugs, prison etc. - and then a comment about deliberately cultivating people with those sorts of relationships!
I know plenty of people who have issues in their families; IME it's just that some may be quieter about it than others, and I'd include my own, wider, family in that.
No one, including me, is suggesting people don't have 'issues in their families', but mydogisthebest's experience of other people's family life as an inevitable fiesta of drugs and prison sentences is neither typical nor any reason to congratulate yourself on managing to avoid that type of thing by not having a child. It would make as much sense for me to congratulate myself on not being a pet owner because I've avoided the possibility of my dog savaging a toddler.
I was happily childfree for far longer than I've been a parent. I remain exactly the same person. Have a child, don't have a child -- it's a moral neutral. Neither decision is superior to the other, unless you are talking about population reduction on environmental grounds. There are no grounds for 'condescension' either way, and the 'parents are superior and pitying of the loveless, empty lives of the childfree' position is as much of a tired old stereotype as the childfree 'tiresome breeders who've lost their individuality and pelvic floors' one.