That's caused by excessive metric tracking on the part of companies, and passing the blame down to individual employees. When a 5-star rating is the default and anything else is a push for the person to be fired, of course people won't leave negative reviews, that's going to prevent people from leaving accurate reviews.
If I could trust reviews to be used in good faith (e.g. by paying employees a living wage and not implicitly requiring dangerous behavior to meet quotas), then I could leave more accurate reviews.
If they were driving recklessly, then they should be fired though. Uber prices are pretty much completely dictated by supply and demand. By taking a higher volume of passengers at the cost of safety, you're increasing the supply of trips and pressuring safer drivers to match your volume. Firing the reckless drivers creates a landscape where safer drivers can fairly compete.
If I could trust reviews to be used in good faith (e.g. by paying employees a living wage and not implicitly requiring dangerous behavior to meet quotas), then I could leave more accurate reviews.