Why do guys would still go out with a girl to dinner and knows he has 0% chance of hooking up with her?

I hear alot from USA guys that they go out to dinner with with girls and spend money on dinner and movies and have no chance with? She told him before hand she wasn't interested in him but will still go out with him? Whats the point besides throwing money away for somebody that's not in to you? Is it just woman companionship? I even hear girls at my job talking to other girls saying, he we went out to dinner last night but i really not into him. So why do american guys go out and spend money on girls whos not interested in them? I told my friend he should save his cash and kick her out and spend it on somebody that at least have some interest in him..