From what I've learnt of business in France, it appears to have a lot of anti-competative laws built in. From talk between British Ex-Pats living out there, it appears most see more benefit working outside the law than in it.
I talked to one guy who ended up going out to work on a guys Chateau to get it out of a weird "uninhabitable" status that houses can get. Apparently the owner started out getting legit french workers, except the plasterers doing the walls suddenly refused to work because they needed some old wiring removed and they're not allowed to do it. The guys said this happened so often he fired them all, came back to the UK and found a bunch of contractors, paid them to drive down and then when they'd finished a months work he paid them back in the UK to avoid money trouble crossing the border.
A guy we met out there works as a handyman, apparently the only one in the area because you have to pay multiple taxes or something stupid to do more than one area of work. So he's "based" in the UK and every six months he goes out to see his kids and travels back to his house in the south of France, "on business". The insane thing about it is that it's perfectly legal in France for the guy to spend 50 weeks there a year, and he doesn't even have to pay the French taxes as he's working in a business loop hole.
Essentially he's working under the contract worker laws, that a Brit can work in France as a reporter or specialist or whatever and not pay taxes as he's working for a British company. The thing is, he's the only person employed in his company and he requires himself to work in France. It's just ludicrous. With the EU how it is, the French builders could just start a business in the UK and do the exact same thing and make more money because UK taxes are lower.
Lots of people 'route around' the French legal system (especially concerning tax and social charges) because it's onerous. This is a classic example of what happens when you introduce a really complex burdening system... people figure out now to ignore it.