He's just telling us what this woman said to him that because the man she was with he was no longer desire love that's why he's saying you have to cheat he's not just saying go cheat listen to the lyrics everyone please this song is deep and she's no longer desire love that's real
So this song is not necessarily giving advice as to what should be done in your relationships but it's basically telling of the older Generations way of doing things. Because the older Generations mind-set especially the females was to maintain a family to maintain a husband and to maintain their children and one of their number one goals was to please their husbands and sometimes they weren't able to completely satisfy their husbands maybe because they were sick, tired,fatigued or whatever the reason and they didn't want the man to get dissatisfied with the marriage and they knew that, that man had certain desires that needed to be fulfilled. And so if that man had to go somewhere else to fulfill those desires that woman may have silently allowed it as long as he came back to her at the end of the day, and they just stayed married no matter what because divorce at that time was frowned upon. Now I don't condone this in any way but I do think this is what the song is relating to us. But i m ay be wrong