"Shut up or leave if you don't like it" is a very bad form of argument imho.
My fellow attendees at these events are in their 30s through 50s (and for all I know, some might be in their 60s or 20s).
I don’t see ageist discrimination around business trips to be honest. If business travel isn’t for you for whatever reason, there are an enormous number of jobs that don’t require or even offer business travel.
For distributed work, I actually think it's really important to budget and plan for F2F events. Again, if you prefer more of a 9-5 5 days limited travel job, maybe don't do that.
If you know ageism is rampant. Perhaps take this into consideration before selecting the tech industry?
There are other industries which are more family friendly. They might not pay as much, but that's the trade-off. You can't have both.
It's not like doing retreats or other things people with families don't like is what causes it to pay more.
There is no obligation (ethically, or legally) for companies to accommodate everyone.
Certain groups, yes. But not everyone.
Vote with your feet.