Indeed, one would know the laws in advance before going into business there. If you can't make it work there, then don't start a business in France, or at all really.
But that said, the psychological aspect of not worrying about your security doesn't really translate into workers who are more "focused". Here in silicon valley, I have many coworkers who obsess about their jobs, while at the same time they could be let go without notice and without further pay. Every year we get some token raise, roughly equal to inflation, while at the same time the company modifies our health care plan to make it cheaper for them, increases our premiums and reduces the stock grants. (There have been pretty significant cuts in stock grants this year across the tech industry, which translates to a pay cut for most of us)