They’re more reliable in more areas. If I lose something, I’ll get it back. The drivers are less likely to be on their phone, and if they are, it takes less effort to get compensated. (Also, pools are cheaper than taxis.)
With most taxi medallions owned by companies as, if not more, abusive than Uber, a congestion charge appears to be the best solution. This would lower supply evenly, letting prices be raised and thus creating room for compensation (and competition for drivers).