When it comes to market viability there will come a time at which companies just pull out because the headache is too much, even if they are somewhat profitable.
FWIW I think this is posturing on Uber/Lyft's behalf, but is almost certainly a sign of future actions if they cannot make the number work.
They would have to invent a new business model to operate with an hourly minimum wage. Currently they demand very little of their drivers since they don't have to pay when the driver doesn't have a client, but add an hourly minimum wage and now they have to manage drivers a lot more to ensure they are worth that pay per hour.
Now they will get replaced by more traditionally run taxi companies that managers their drivers tighter.
Edit: Or no, the law explicitly said how much ride shares should pay per mile and per minute riding. So scratch that, not sure why they pulled out here.
FWIW I think this is posturing on Uber/Lyft's behalf, but is almost certainly a sign of future actions if they cannot make the number work.