Yep. Flyer you make great points. Many like you mentioned stay for a few years but end up coming back to the USA.
The thing is that for many people it seems glamorous or really cost effective which it can be. But after a while many of these people have most of their family or friends back in the USA. So some of them want to move back closer to grandkids, kids, etc.
One piece of advice I’d have for anyone even thinking about it is get totally fluent in the local language. I can’t tell you how many retirees I’ve met down in various countries that never learned Spanish or Portuguese (for Brazil). Lifestyle and quality of life is MUCH better once you learn the language.
It always amazed me when I would meet retirees that moved to X country and lived there for many years and could only say “hola, adios, or cuanto cuesta” in years of living there.