The taxis did not circle the streets. That was part of the problem. Unless you were walking out of the lobby of a downtown hotel, there was basically no chance of catching a cab in SF. The wait time for calling for a ride has been lowered from "never" to "3 minutes".
Uber/Lyft definitely have increased the growth of riders. I use both regularly and way more than I ever used cabs because it's cheaper, easier, and more reliable to use them.
There's been shift from public transit to rideshare - when an Uberpool is $3.50 and the bus is $2.25, a lot people are going to switch to Uberpool.
All that said, it seems like there are basically two sources of congestion in SF these days, and neither of them are rideshares:
- the Bay Bridge, which backs up all the way up 1st, on to Bush and Battery, also down Bryant, also a couple of blocks of Harrison, and the central connector/Octavia/Oak street, every damn day. There are just a lot of people trying to get to the East Bay every day between 4 and 7. Also, BART is full. There is no cheap, quick solution to this. A second BART tube would help.
- everything for a couple of blocks around Union Square and Moscone is a mess. Everyone with an ounce of sense takes Muni here already, it's very heavily served by public transit. Once again, this is a centrally located area with a ton of hotels and a major convention center. If they got rid of all the rideshares tomorrow, more people would just drive to get here instead of taking Muni to get here, and traffic would be the same.
While the double-parking is annoying, it's not actually what's increasing congestion in SF. The biggest traffic problem in SF is that they didn't start building a second Transbay Tube 15 years ago.