It's true that the EU has no federal executive body, however, no country can simply go and set corporate taxes to 0 without an uproar. the cross border phone network is unified for example. The were Cyprus and Malta selling passports to the highest bidders without due diligence done,kickbacks and honey traps, you name it, it happened. https://euobserver.com/justice/149810

There is a limit on how much can and can't be done within the EU, it's not a gravy train buffet. There is peer pressure and potential, let's call it cascading effect. Some lawmaker will hear about this and try to get it passed in another country as well. I struggle to think of one state which would simply accept Uber as some great Enterprise idea, look at the history here https://en.m.wikipedia.org/wiki/Legality_of_ridesharing_comp... Most places banned and this bit. In December 2017, the European Court of Justice ruled that Uber is a transport company, subject to local transport regulation in European Union member states, rather than an information society service as Uber had argued.[99]

So at best, tolerated for the time being.

In Europe, working without full compensation is typically called illicit work(instead of side gig), not extremely frowned upon, but the main job has to have proper compensation. It very normal and expected to get 4 weeks paid holidays or more, sick days covered, insurance in most places, pension contributions etc. Uber tells you to get a car, petrol, pay insurance and take jobs when available, and get none of the above, who are they kidding.