There's no "backing out" if we're talking about individual cities in a country they already operate in (save a few edge cases). That isn't really how Uber/Lyft enter/exit markets. They will just not pay driver incentives for new markets, which is usually the lighter fire for incentivizing new supply (i.e. drivers) to start driving.

There's no job to be "lost." They aren't going to turn you away for a "job" or "fire" you because you literally aren't employed by the company. Think of it as if you are licensing Uber/Lyft software to generate leads for your own business. That is literally how they think about it and what the driver ToS says.

That’s true, there’s no real reason to “leave” a city. But if they need to stop bleeding cash in an expensive city, they’ll need to raise prices during a hurting economy. Doing this at scale is going to severely dent their ability to cover fixed costs long term.