[quadrige]

Airbnb socializes the costs by transfering them to the flat owners (cleaning etc.), and Uber to the drivers (fuel, maintenance etc.)

[krrrh]

In terms of Airbnb socializing costs, it's not the flat owner who is taking on some costs and some profit, but their neighbours, who bear the costs of noise and reduced security and community.

[wyager]

That's not what socializing means. Socializing means using government to redistribute costs to the population at large via taxes. Entering a voluntary private agreement where you have some obligations is not "socialization".