After you "link your Visa card", yet the reward is in "Waymo cash", which expires in 90 days and can only be used for Waymo. That's just something on your Waymo account, not real money. They must want access to your Visa card data.
I've seen Visa branded ads for some e-payment solution in a South-East Asian country. The solution worked with any credit card, but the flyers were clearly Visa marketing material.
Not sure how it works in SF, but many cities across the world have moved to "in-card tickets." You tap your card on the way in, and the bus "knows" that this card number has a valid ticket attached to it. Depending on the particulars of the city and system, you might need to tap out too.
In some cities, this is done entirely offline. For cards which cannot guarantee offline payments (which many low-income / under-age individuals have, and such people are far more likely to use transit), this is done "on trust", with failed payments getting your card blacklisted until you go to the transit agency's office and get the situation rectified.
At least in the NYC MTA's OMNY, unblocking actually happens automatically in the background, either on a nightly reconciliation job that attempts to collect your fare or triggered by the next tap (which will be unsuccessful once more but trigger the collection attempt, and then you can tap again after your card's blocked status has cleared in the system). They also have a website to manually repay without having to wait at the turnstile.
It will never work in a punishment-oriented society because you're very likely to get away with riding for free if you don't do it regularly, and these societies feel that catching the bad guys is more important than working well for the good guys.
It's compatible with a card payment system but then proving criminal intent to free-ride is harder because the system gets complicated for the user. It's great with a paper concession ticket.
Also, the experience of riding Bart seems to have improved quite a bit since they installed better turnstiles, and that likely will affect ridership numbers.
Why not fund public works through taxes and let everyone use it freely? Do you prefer toll roads and going through a toll over literally all the other roads that have no fare? Are roads worse because stupid and poor people can use them too?
Oh, and funny note, most toll roads in the US are in a weird system where you paid for it's construction with your taxes and then that infrastructure is basically gifted to a company.
Fareless options have been tried before and it comes out to that it makes problems with antisocial behaviour even worse. So I'd say we should just charge fares that cover actual costs, and then for people who can't afford that, provide subsidised fares.
The other method of suppressing quality of life crimes and fare evasion is lots of transit cops. It's probably cheaper to install the gates than hire lots of transit cops and arresting people over fare evasion makes the city/transit agency look like bad guys.
OR, if it's Visa only, it's a comarketing stunt.