That is one of several possible configurations of the society. That's how it works when colonists arrive and set up first villages. They buy and sell directly, treating each other as individuals, not as companies.
However today France - and any other modern country - is not set up that way. It has a government, and that government is tasked with collecting money from taxpayers and spending it on defense, on social security, or - among other programs - on spaceflight. Taxpayers are individuals and businesses.
Uber apparently is skipping the obligations of a business, but enjoying the privileges. Paying the taxes is just one, most obvious aspect of it. But I'm sure there are more. How about business insurance? Does the driver carry a business policy, one that will be valid if he has an accident while transporting people for profit? How about work hours? How about making sure that his car is checked by a mechanic every day? (Or, does the passenger want to ride in a car that makes one million miles per year but rarely gets checked?) Does the vehicle's design protect the rider from the driver, and vice versa?
The business license may look like a bureaucratic excuse for grabbing some money, but *in this world* it is also a stabilizing factor. If you buy a pizza, you can be more or less sure that it is made in sanitary conditions, from fresh ingredients. That's one aspect of regulation - enforcement of some standards that are required for safety.
I can definitely see that Uber is a disruptive technology. Taxicab drivers were always a special club that is expensive (or impossible) to enter. Cities used sales of permits (medallions) to raise lots of money. Cab companies and drivers then charged the riders with high fees to cover these costs and enjoyed their monopoly position. Uber makes them all obsolete. The problem is not with old companies, and not with new companies, but with the fact that both exist in the same space and at the same time.
Once the industry "matures" it is likely to disappear, because sooner or later either the workers will figure out that it isn't worth it, and/or the customers will be forced to pay the true cost of the service.
When our colonies matured to a nation, I believe tariffs and real estate taxes paid our bills. Our cities, counties, states etc have become too thirsty for tax dollars. And why would Uber pay a business tax in a city, when it uses none of its services for a ohysical presence. The drivers pay their gas taxes for their use of the roads.
In France, Uber has been providing the additional insurance coverage. My understanding is this varies widely depending on local rules.
As far as safety etc are concerned....people can make their own choices. I may never take an Uber ride...my choice...but other people are grown up enough to make their own decision.
Cabs have been magnets for graft for decades. Im glad something is upending it.