I think you have this backwards. In the emotional sense, cheating is something that evokes a feeling of betrayal when discovered: "you went behind my back to fuck that other woman, even though I was faithful to you". If A loves B, but B doesn't love A, and then B sleeps with C, then A will still feel betrayed.
As another user said, people stay in relationships for reasons besides love all the time. A cheating husband has incentive to hide the cheating and stay married, if his wife cooks, cleans and raises his children for him. A housewife who cheats has a lot to lose from a divorce if she financially depends on her husband. And so on. There are even "people" who string along multiple partners at the same time, not because of love, but because it makes them feel powerful, and gives them easy access to several warm bodies to exploit.