For regular work visas, the idea is to attract labor force that will be able to work a full career. In many places retirement terms are fairly generous and I’m guessing a lower level foreign employee who only worked the minimum years could be a net negative to the system.

They can do proof of stake, where some kind of wealth is directly or indirectly demonstrated.

For example, the Cayman Islands had a pandemic program that required staying at certain bubble properties, which were like $10,000 per interval. Not sure what the interval was, but it was expensive and would accomplish the gatekeeping.

Money to spend, they care less than having young, cheap-enough, able to make children, might go back home easily in case of trouble immigrants.

I immigrated in my current country at 26 and it was really easy and warm, and they did everything to quadruple my salary from the european country I came from.

Now that I'm close to permanent residency and 33, I'm thinking of jumping again, but with a kid, an giganormous salary and a lot of money to be picky, I expect to be more a burden for the next country than an obvious cheap asset.