The problem with rating systems for traditional taxi-services is that they are most often without effect. There is no penalty or change if a driver is rated badly.
Actually it's not the case. Not only drivers have to have a good rating to get rides off-peak, the app operator also serves as an effective complaint outlet. I've heard of cases of people complaining to Hailo about a bad ride and getting their money back. I guess the taxi drivers accept to pay back, because it's still better than losing all these future rides.