* The medallion system gives owners something significant to lose it they become scofflaws, and while we all have horror stories about cab drivers, anyone who's traveled to Asia (or, for that matter, Italy) knows that we have relatively well-behaved drivers, even in the cohorts selected for worst incentives.
* The taxi companies are required to comply with rules that make taxis part of the fabric of transportation for the whole city (for instance, they're usually required to serve every destination within the city). Uber does not need to comply with these rules, and thus threatens not just cab companies but the transportation system as a whole.
People's homes are a pretty big issue in when threatened by neighbors that can destroy everything you own. People get the possibility of a car accident even if it can be much, much worse.
1) credit check & renter history are standard
I would imagine that each landlord and each homeowner's association could come to their own agreements on what is and is not acceptable without the need for laws on the books.
I get the feeling it is more the origin of the law as a business regulation that drives the criminal part. I too wish more things were handled as basic contract law issues.
Black and Jewish folks used to have a hell of a time getting a hotel room in the US at various points in history. That became illegal with the 1960s civil rights laws, but recent media coverage suggests discrimination is rampant on Airbnb.
It also used to be nearly impossible to find wheelchair-accessible hotels.
I have no idea what the solution is here, but there are good things about regulation of these kinds of businesses.
We have the same problem here in Austin, except it is Taxis being protected against private drivers like Uber and Lyft. They claim this is to protect citizens from unlicensed drivers.