Uber is more for quick short journeys where you jump in and jump out. The more quick short journeys the driver makes the more money they earn. You won’t be ripped off as you pay through the app – no need to exchange money or even conversation with the driver.
Ideal for mooching around san francisco as a tourist or a lift home from the pub. I’ve used Uber a lot in the USA, Vienna, Lisbon, London etc. Its fantastic because you don’t need to know where you are or where you are going – you set it in the app using gps and on a map – this is downloaded to the driver. You don’t need to negotiate payment, all done through app, and it shows you the driver approaching their car make and model and reg number.
Its not really appropriate for airport runs where you spend 10 minutes loading up massive suitcases. The driver will not like this, and if they spot you with massive suitcases might even drive on by without picking you up.
If the stuff you are carrying is in your hand and ill sit on your knee then use Uber. Otherwise you need a taxi.