Question about Fantasy

Hi guys 25m cuck here my biggest fantasy I always masturbate to the thought of my wife getting bred and impregnated by her BF and then me being denied her pussy and locked up and made into just a cum cleaner and house wife for them.

Obviously this is just a fantasy and I don’t think I could go through with it in the long term irl and I wouldn’t want to I don’t think it’s okay to bring kids into this work just for a kink, you know?

Anyways my question is, is there any reasoning behind why some cucks like me fantasize about this or more so why some actually choose to go through with it? Like why does it make me so much hornier and increase my load size when I think about?

And I mean I realize some do it for medical or biological reasons of course. But if everything is working perfectly down there then why let another man do it?

-My wife does currently have a BF and has an IUD and he fills her every time they’re together multiple times even it’s actually impressive.