In general, the ability to know beforehand the price, is golden!
Adding to this: in countries payment can also be a problem, trivially solved via Uber. Take e.g. when I first arrived in South Korea and took an cab from the airport (fixed rates and in cabs in Korea are nice, so not a complaint there), the taxi couldn't take my card, and I didn't have 100k won in cash (accidentally took a luxury cab), so we had to drive around to find a bank that luckily took VISA.
Japan: Works great Turkey: Nope. Thailand: Nope. France: Works, but not always well
In a lot of countries, cab drivers are illiterate. And I don't mean functionally illiterate. I mean simply CAN NOT read. Not even a map. If you don't speak the language absolutely fluently, you're screwed.