Probably most of the people who voted for the tax don't ride Lyft or Uber so they won't pay it.
Half of the money raised will go to adding more transit service. The rest will go to various traffic safety improvements.
Cab drivers used to be union members with good paying jobs and benefits until the 1970's? when the cab companies forced them to become independent contractors and lease the cabs from their companies.
Their working conditions are just as bad as the ride share operators but the companies and
many cab drivers don't want to be regular employees again because they are afraid it will make the cost of a ride too expensive for many people.
In SF long before Lyft and Uber were around the cab companies and drivers consistently opposed issuance of more medallions (which are basically permits to operate a cab) because they thought it would put too many cabs on the street.
Many neighborhoods had very poor service because the cabs tended to serve more lucrative hotel to and from airport trios.
Because cab drivers took cash fares they basically refused to accept rides to low income minority neighborhoods because they were afraid of being robbed.
Now Lyft and Uber have so many drivers,it only takes a couple minutes to get one anywhere even in the middle of the night.
If there was no Lyft or Uber and the city still attracted tech companies with many people who don't own cars and don't like riding public transit the cab companies would have to add more of them and people would complain about too many cabs on the street.