We all seen the reactions nice people have when they are tired of being taken advantage of or casted to the side. Telling them, "if you expect a reward for being nice, then you're not a nice person." Is nothing more than gaslighting someone who just wants to be respected. Now I know there are guys and girls who place nice just to sleep with someone, I'm not talking about them. I'm only talking about the genuinely nice people.
If someone is nice to you, you should be kind to them. Everyone is so fixated on having attitudes all the time and lose common sense when it comes to someone being kind to them. Someone being nice to you isn't flirting with you at all.