Medallion systems often prevented any competition, sometimes to absurd effect. The number of licenced taxis often didn't keep pace with population growth, sometimes even staying flat. Many drivers didn't own their own medallians then had to rent from owners, often making little money. In my city (Toronto) cabs were often dirty, broken, refused short distance fares (illegal) and smelled of cigarette smoke that was obviously from the driver.
Examples (paywalls, but you get the idea):
https://www.nytimes.com/1992/07/26/nyregion/amid-a-heritage-...
https://www.theglobeandmail.com/globe-drive/adventure/red-li...