Before limits, drivers couldn't earn a living. Not legally at any rate. And once some people started to cut corners and break laws, everyone had to or they would go out of business.
Some scarcity meant that the cab drivers could comfortable follow the law, comply with regulations and have a reasonable expectation that they would earn a living income. Net result: safer streets, safer passengers, safer drivers.
You might plausibly have an argument that cabs are too scarce, but I think that anyone who understand the 'before' and the motivations behind the allocations will see that it's the least bad option.