Most Helpful Guy
I'd guess because they are fucking cunts and they have lost their "LOVE" with her or him but are too scared to end it.
Most Helpful Girl
Well the thing is... i feel like some people only think with their body. Like it's all about physical attraction and nothing else.. you see I got a friend who dates guys without knowing them before, just cause she finds them attractive. And during the relationship she's like "omg I love him" so yea in her mind she thinks that it's love but it definitely isn't. That's just physical attraction. But the thing is, despite this fact, she still gets involved in the relationship and all, and when she finds someone else she will simply be like "I think I don't love my boyfriend anymore". So she cries, breaks up, and after a few weeks she will just find someone else. So what I'm trying to say is that well for now she doesn't cheat on her boyfriend. But I am convinced that when she will be older and feel like she "has to" build a stable relationship, she will end up in this situation where she thinks she loves her boyfriend but also feel attracted to other men too. And one day or another, she would just cheat on him. So yea I was just trying to answer your post with an example... dunno if it was understandable tho haha