I think it's an age thing yeah, but also it just comes down to circumstances. Id imagine that the people who are just packing up and moving to different countries every year for work don't have a large family/friends support network around them
For me, moving to a different country would be a nightmare in more ways than I can count, I've got pets I'd have to arrange transport for, a wife I'd have to get on board (can't even imagine if I had kids), all our family and friends are from the state we live in today.
But if you already had family/friends in that country, or if you were solo and your fakily/friends were already a distance away, then it wouldn't be so bad