You can, nobody is stopping you. But if he charges you for it he will be encroaching on the taxi drivers' turf and cutting the city out of its share of the loot and for that he will be fined and/or imprisoned.
Occupational licencing in almost every case is nothing but a racket to artificially limit the number of practitioners and keep the prices high and to collect a tax by a different name. At least you can make a bogus safety argument when it comes to driving, but what about hairdressers, photographers, interior designers etc etc all of whom require a licence in many jurisdictions and who have to pay the city or the state an annual hefty fee in addition to taking useless courses and passing tests (more fees) in order to be able to work, despite the fact that many other jurisdictions don't have those requirements with provably zero ill effects. 1 in 3 Americans today are not allowed to work in their profession without a government license.