Not OP, but I work in the industry. It's not as simple as opening the tap for three primary reasons: 1) localization, 2) operations, 3) cost.
Localization means that you cannot generally (with current-state tech) ship a bunch of cars to a new city and turn them loose. You have to do a large amount of detailed mapping, characterization, and training in every area you want to launch. That's why you see all the self-driving companies slowly expanding availability areas after their test cars have been running around for many thousands of miles in the area.
Operations is all the stuff that's not the car driving itself around. The cars need a home base where they can park when not in use, recharge, get cleaned, have sensors checked and calibrated, and get maintenance when needed (scales linearly with number of vehicles). The cars are also not 100% flawlessly handling every situation and rider issue - there still needs to be human support in the loop, both in terms of a dedicated remote support team (scales linearly with number of rides) and in terms of local rescue people to get cars when they're really stuck (scales linearly with number of vehicles).
Cost is the cost of vehicles, tech (ADKs), and operations. Waymo and Cruise are currently operating at absolutely massive loss and will continue to do so for years. It's generally not a great idea to open the faucet on a money-losing business until you at least have a solid way to get to profitability. Yes, I know, Uber and other giant startups basically never made money, etc. etc. but the market has changed and owners are looking to decrease costs of tech and operations before really scaling up. It's going to take a couple years still.