It's because "the unions" is colloquial shorthand for "labor unions" which, whatever their plusses and minuses might be, are a very different concept than `taxi unions'
Because of this muddled terminology (and probably because suggesting a single source here is obvious oversimplification) you sound like you don't know what you are talking about and are just typing a screed. Hence the downvotes.
I think you are smarter than that, and can find a more articulate approach.
Your comments are grey because your statements are completely ignorant.
Major cities instituted a medallion system for taxi, restricting who could operate a taxi service. The owners of the cab companies in major cities bribed the local governments into limiting the number of medallions in circulation, then bought all of the medallions. Meaning that cab companies have government-sanctioned monopolies on taxi service in many major metro areas of the US.
As others stated, this is an example of a cartel, not a labor union. And the entire purpose of cartels is to maintain artificially high prices.
