To respond to the original comment, the notion that your tip goes to the driver and the rest goes to the cab company is sorely outdated.  That system went away a quarter century ago or better.  Go read the Wage and Hour Act a little more carefully, as that law is a factor in this issue as a whole.

Responding to the other part, liquor licenses are limited.  In many cases, they carry a speculative value far exceeding that of taxi permits.  You would see a lot fewer liquor licenses operating if not for the fact that many of those licenses enjoy grandfather rights, in some cases stretching back before statehood.