So he died, because for a split second he got brave. But not then. He died much later, after the split second of bravery had faded into long hours of… - Lee Child

The guy that was standing said, "We don't want you here."
Reacher said, "You're confusing me with someone who gives a shit what you want."
"You won't get served in here."
"Won't I?"
"Not a hope."
"You could order for me."
"And then what?"
"Then I could eat your lunch."

The world is the same jungle all over, but New York is its purest distillation. What is useful elsewhere is vital in the big city. You see four guys bunched on a corner waiting for you, you either run like hell in the opposite direction without hesitation, or you keep on walking without slowing down or speeding up or breaking stride. You look ahead with studied neutrality, you check their faces, you look away , like you're saying, Is that all you got?
Truth is, it's smarter to run. The best fight is the one you don't have. But I have never claimed to be smart. Just obstinate, and occasionally bad-tempered. Some guys kick cats. I keep walking.

People have their reasons for giving rides, all of them different. Maybe they hitched a lot when they were younger and now they're settled and comfortable they want to put back what they took out. Like a circular thing. Maybe they have charitable natures. Or maybe they're just lonely and want a little conversation.