Uber, represented in the hearing by high-priced attorneys, did not apparently bring up the idea that the Plaintiff could have (or should have) worked simultaneously for other car service apps. Presumably there were legal reasons why that argument wasn't compelling.
But taking a step back, though it does seem to be a vaguely mitigating factor, maybe, in the abstract, the fact is that this woman wasn't a contractor by the legal definition.
The law doesn't say that employee/employer relationships are determined by what could have happened in some alternate universe. There are full time employee plumbers and carpenters and programmers, and contractor plumbers and carpenters and programmers. They use multi-part tests and precedent to determine which is which.
The determination was that this woman was -- in fact - an employee, it was not a hearing to determine a hypothetical scenario.
Somewhere in California there may be an Uber driver with a fact pattern that makes them a contractor, or not, but it'll take more cases to figure that out.