The other ride hailing apps are in the business of selling hailing services to taxi firms and have sales teams dedicated to doing so, are not despised by taxi firms, and provide solutions optimised for regulated taxi firms. If they tend to provide surprisingly few drivers and poor price estimations and the app companies are orders of magnitude smaller in terms of revenue and geographic spread, that's probably an indication the licensed-partnerships-with-cab-firms market is more awkward and less lucrative than it sounds.

And the taxi firms usually won't and often legally can't use Uber's pricing algorithms which is pretty much the only secret sauce to the app, they don't want to ignore bylaws that Uber has cheerfully skirted around and they don't want their expensively-licensed drivers competing for leads on an equal footing with new Uber drivers.