I actually do think cabs are broken. Without a rating system after they get a medallion they're golden for at least a year.

I get into cabs where: - The driver can't speak English - Doesn't know where they're going - The cab smells - Drives dangerously - Is drunk (literally had an open bottle of wine under the handbrake) - Doesn't turn up when I book it

The list goes on, the moment I started taking uber cabs all of this stopped, I review every cab I take after a trip and the moment they drop too far they're removed from the service.

Sure, maybe within the existing system I could write an email to the cab company (who will probably ignore me on account of trying to avoid a fine), the medallion issuer (who MIGHT fine the driver if this happens often). But the reality is that this is hard, and giving someone a rating between 1-5 stars at the end of the trip is easy.