I'm with the "It's easier after 50" group, but I think some if it is changes in the economy.
I don't really see any health issues. I've generally commuted, and done a few weekend trips, so for the long tour with no fixed schedule, it was easy to just start slow and get back in shape along the way.
I think there is more contracting/gig economy now than there was 25 years ago. In the 90's it would have been much harder for me to explain quitting a stable (at the time) job, and expecting employers to understand if I wanted to find another one when I came back. Now none of the jobs are stable, so it's not hard to take some time off between contracts.