In France if, for an average employee, you add the employer and employee contribution to social security, for 40 years, you find that it pays two large houses.

At the same time most average employees will struggle to buy a house.

And the social security will reimburse well only medical costs (visit to family doctors or medical acts done in hospitals). For other costs, hospital care, glasses, dental or hearing costs, it reimburses very little.

So for me France's SS is actually a kind of mandatory way to channel money towards doctors.

Lets assume that instead that money would go to the employee and not to social security. And we will assume that a large house would cost about 500k EUR. Thus, in 40 years, you would have collected a million euros more. That is about 25k EUR extra per year. That seems to be about the amount of income tax a French citizen would pay every year.

Thus, that money doesn't just go to health care. It also goes to other social security programs and government projects.

I thought France has a rental culture, no?

I'd rather be alive and renting than dead with an estate that has ownership of a building.