Sincere question: I wonder how you'll feel in 30 or 40 years. I have an extremely smart, distant-relative-by-marriage who's in his late 60s; he dotes on his two middle-aged nephews and their young families — my speculation is that, as he has developed some health problems, he's come to realize that they're all he has for his old age.
Either way, if I had children, I wouldn't think it right or just to burden them with an expectation that they owe me endless years of emotional, physical, or social support.
Additionally, I think our brains are very good at rationalizing and justifying the choices we already have made, and so I'd mostly suspect that I'll continue to convince myself that I made the right choice regardless of any loneliness that may crop up later in life.
It also might seem callous, but there are simple psychological needs (such as feeling that you're caring or providing for another being) that are easily fulfilled without having children. Pets help a lot. Volunteering helps as well. And, of course, just like your older relative, spending time around other children and young people when you can.
My hope is that between all of these things, I'll lead a happy and fulfilling life. Or maybe I won't – but I ultimately don't have any control over that. And my personal opinion is that having children doesn't assure you a fulfilling life either!
Just throwing this out there - I 100% agree with you but anecdotally find that older generations see this completely different. There's an expectation/entitlement there of "we raised you, so you owe us this..."
It's even more rude to attack someone's sincere attempt to elicit discussion about a serious matter.