I have used a taxi once or twice in Berlin when arriving at the old airport (Tegel) and not wanting to use the bus. The transit system is extensive (S Bahn, U Bahn, Bus, Tram) and its easy to get anywhere you want to go.

Uber simply summoned a taxi when I was there, It might have changed. But with the new airport connected via S Bahn, I don't think I will incur the expense.