But pretty logical, no? You don't want someone to migrate to your country in his late 50's / early 60's, contribute to your economy for a few token years and then piggyback on your medical welfare system for rest of 15-20 years. Whats the incentive for local citizens to welcome immigrants in that case? (And no, I don't want to consider rare examples of superstars in their 60's. I am just talking about average Joe's).

Some studies (search Google) have shown the average age of an entrepreneur is around 40. And I'd like to see the backlash the US would get from the world if they implemented many of these criteria.

Canada has a separate visa process for entrepreneurs:

http://www.cic.gc.ca/english/resources/publications/entrepre...

The program being cited is for workers, similar to the US H1B. And others have addressed why age is a sensible factor.

You can't get social security unless you pay in for a sufficient number of years

But that's not the only program. You can get Supplemental Security Income without even being a citizen or ever having paid in.

https://www.ssa.gov/ssi/spotlights/spot-non-citizens.htm

Also you can generally get Medicare if you're old and you've paid in for a few years.

It makes some sense as a way to weight for "promise". Many of the other factors (level of education, language ability, work experience) are measuring things that an older candidate will be more likely to have already, but which a younger candidate may be more easily able to acquire after immigrating.