I don't feel like reverse-rating systems are actually a good idea without some checks and balances. You have no way to know how a driver decides whether or not to give a passenger a bad rating. We know from history (both pre-and-post-Uber) that sometimes drivers have an agenda in how they treat their passengers, either due to race, gender, or other factors, just like how sometimes a horrible passenger will mistreat a driver.

With driver ratings, I can see my driver's rating and they can see it too. The rating system in Lyft (not sure about Uber) also has buttons you can use to explain why you gave a bad rating or indicate what you liked about a driver, which presumably provides anonymous feedback to the driver on how they could improve their scores.

In comparison, a passenger with bad driver ratings gets no feedback or incentive to improve, and it's hard to know whether they could improve at all. If they have a bad rating from drivers they may never know and will just have a bad experience with the app, potentially forever. If you pick up a fare who already has a rating of 1.5/5, are you more likely to negatively interpret their behavior and give them a low score? Psychology is a factor here.

An anecdote: On my third ever ride with Uber, the driver told me I had a very, very low passenger score. That means one of my first drivers gave me a low rating, probably a 1 or 2. Why? I have no idea. He didn't know either. Maybe the driver was having a bad day or thought I was rude, or the driver had trouble finding my pick-up location. In the end the only outcome was that it took me longer to get a driver to pick me up afterward because drivers saw my low score. (I use Lyft now instead and have no problems)