Because

1) People don't understand the true costs of ownership and driving and think they are yielding the entire cost of the fair.

Or

2) They enjoy driving, getting paid for it is a bonus.

Or

3) They don't/can't have "regular employment" for whatever reason and want to make some money in their spare time, even if it's just a little. Like some in college who only works during breaks or weeks when the courseload is smaller.

Or

4) Someone who is employed but only drives when they are bored on the weekends rather than watching Netflix or going to the pub.

Of course #3 becomes self perpetuating at scale.

For #1 - story time: I had already decided I was going to buy a new car, which car I would buy, and that I was going to finance it. I was trying to squeeze another year out of my current car first tho. My sister was absolutely baffled by this and couldn't understand that this would save me money. No matter how much I tried to explain it she didn't "get" it.

From TFA: >"Imagine developing a company specifically to take advantage of people’s ignorance of how expensive it really is to drive their own car. What would this company look like?“ (the answer is of course that it would look like very much like Uber or any other ridesharing company)