> Uber says there is a surplus, people driving cars with empty seats, and they attempt to capture that surplus. From an economic point-of-view that is a good argument. The surplus undeniably exists, and it would be beneficial to reduce it.

This is actually not what Uber says. Ride-Sharing would be fully valid as long as the fee paid is lower than the cost for the car owner. It's specifically exempt from the law. However, the fee that Uber proposes is far above the accepted costs per kilometer (it's roughly 1 EUR, while the accepted costs are roughly 30cent), so they don't qualify. There's a german startup (Wundercar) that tries to capture specifically that market and they just reduced their prices in response to a similar injunction.