You have to pay a human to take you. Humans are expensive.

and smelly, and talk too much, and the biggest one of all: suck at driving.

The human part is pretty cheap compared to the other parts at least here in Toronto:

Car insurance $220 (20h at minimum wage)

Car payment $780 (70h at minimum wage)

Gas $200 (18h at minimum wage)

Parking $250 (22h at minimum wage)

If I didn't enjoy driving and having a nice car, it would already be cheaper to Uber everywhere.

$780/m lease is payment for 6 years pays for 60k car. More realistic lease payment is $200-$250/m.

Average insurance in US is ~$100/m

Maybe I'm getting confused due to currency changes, but I think you could certainly divide all of those numbers by two in many American markets.

This is the right answer

Because Humans quickly change your rider review from 5 stars to one when you do not tip.

Drivers have to rate you before they see your tip unless you give a cash tip.

There have been reports of drivers changing ratings retroactively after seeing their own rating drop, or if a customer doesn't tip.

Autonomous cars should be a cheaper than Uber eventually. Additionally I imagine they will be more reliable, which is something you can't necessarily guarantee with a random uber driver.