You are taking the exactly correct way to think about savings: asset-liability matching, and being realistic about it (not imagining you can move to a new place because 'retired', so do, but many can not do so successfully).

But many can, and do. To each their own.

Indeed. But shouldn't assume the can, because that kind of assumption something many cannot survive.

Sensible planning is asset-liability matching.

But the win in that game is to save 10k per year in the US, then retire in Europe. Get full retirement in half the time.

Many do that within the US with cost of living games. Work in SF for 5 years saving 200k a year. Move to Flordia and be set living in 40k a year for life. (Or some variation thereof)

That works for some. But there is a loss of social capital and cultural capital in moving. Over a few years it's possible to build a new friendship circle (although I'm told that gets harder as one gets older). Additionally, while a basket of goods might be cheaper in Florida, as Rumsfeld said, there are unknown unknowns.

Perhaps Florida is more expensive than you might think because the cost of air-conditioning is expensive. And while lots can go without it, as a non-native, you might find the heat unbearable. I'm using this as an example of why it's difficult to estimate the true costs of living somewhere until you've put down roots there.

Furthermore, when you're on 100k a year and saving $10k, spending $400 on a new phone is a negligible expense. If you're on $30k, and saving $6k it is a bigger proportion of your savings. If you plan on moving, you're going to readjust your standard of living and your creature comforts.

Obviously your strategy can and does work, but counting on a move working out and being able to reduce living costs is a riskier strategy (with a potentially bigger payout), and it comes with its own costs.