I can't speak for others, just my situation. We did not start out w/a cuck relationship. At least not a recognized one. We met via a swinger couple who knew I was looking to just meet new folks w/'varied' interests after my divorce. He was into crossdressing at that time, or actually coming out of a cycle of it. (for us our kinks tend to run cyclical hehe) Anyway, for a long time we were hardcore D/s. He was the Dominant-sadist and I was the submissive-masochist that he shared w/any cock he wanted. Over the years he encouraged me to go into escort work and loved the idea of me getting all my holes filled regularly. He even wanted me to find a regular or two to have clean, messy sex with so he could clean me up afterwards. He then found cuckolding sites and all I can say it was history from there.
I have to also say that though I am at my heart still a submissive to him I am thoroughly enjoying being more dominant in our relationship. Cuckolding has given my Sadistic/dominant leanings a space to explore w/in, (in addition to the escorting, I do love my submissive dates hehe)
Now Why do I stay w/him? Because I love him plain and simple. I have a reg BF who I have discussed what it would be like to be w/just him and travel and such but it would entail not having my husband anymore and I love him and plan to spend to the rest of my life w/him. Plus if something was to happen to my hubby and my BF was still around I'd take him up on his offer but I'd have to leave my cuckoldress ways behind me. And no one here wants that now...
I am a truly blessed Lady who is still learning and enjoying myself immensely at my hubby's expense. :) I love a cuckolded husband.