As a 22 year old, you are unlikely to suffer congestive heart failure. But you also clearly have no idea what it costs to get hit by a car, to have a sudden unexplained seizure, or a burst appendix.
The problem with health care isn't that perscriptions cost to much or that it costs too much to see a doctor. Any of us can pay for a doctor's visit. The problem is that a 4-night stay at hospital will bankrupt you.
If you mean that most young people in the developed world (who've been delivered by trained midwives, checked over by a doctor at birth, had all their vaccinations, regular eye tests and dental checkups, and managed not to break a bone during childhood or adolescence) generally haven't needed to see a doctor or go to hospital for urgent medical attention, then you've got a point.
Of course, as they get older, they'll almost certainly need some sort of medical treatment.
You may have to pay for recurring prescriptions. The birth of a child, and many other things that will surely become necessities.
Why not look to those countries and see if they have more startups?
I doubt health care is the reason it's harder to start up in France.