Well I can only tell you my experience. For me, there are two distinct ways to have sex, one is with feelings for someone I'm in love with, the other is the casual one. For me I like getting to know someone in such an intimate level. To open myself and share fun, pleasure and excitement with someone else. It's actually one of my favourite ways to get to know people (I know you are probably shaking your head at this) because at least for me I love the talk before and after (between?) sex, it's often deep and very open, lying there naked with a stranger having just shared your bodies together is really opening. I also like to experience my own and others bodies, and probably most of all I love seeing someone enjoy themselves sexually, it's something so raw and unfiltered about hearing the quickened breath, feeling the muscles twitch and seeing them lose control of their bodies in a moment of ecstacy. And sometimes you really click, and every time you so it, it becomes better. It's fun!