I think an Uber driver's union would be fucking awesome.
Also fucking useless as there's nothing preventing scabbing.
That's the thing about the gig economy - if you're in it, that means you're willing to take the job for shitty pay with no benefits and no security. You are, by definition, cheaper and worse than the people who won't work gig-to-gig. And I say that as a freelancer - a union freelancer, in a skilled position, in a highly-regimented Union profession.
I've gotten thousands of dollars of work redoing bullshit that people think they could get some Mandy loser to do for them for less, and they ended up paying twice.