Unless she initiates the flirting, and does so enthusiastically, an Uber driver should assume that a female passenger is in the vehicle because she needs transportation, not a date.
Attraction and flirting are natural and healthy expressions of human sexuality and not something to be ashamed of.
There’s an ocean of difference between being ashamed to feel attraction, vs. refraining from acting on that attraction because it’s neither the time nor the place to do otherwise. The fact that so many men can’t tell the difference is the reason why it’s better for the Uber driver to err on the side of caution.
Feeling an attraction to someone does not, by itself, give a person license to act on that attraction. The world, and the people in it, have agency as separate human beings. They don’t exist merely as a repository for men’s feelings.