Yeah, I guess this is the cuck side of "sperm competition". Submissive men want to live out the social role they're programmed to accept.To be fair, there is also the dominant that is in fact very secure and wants other partners. This typically falls into the stag / vixen group, not cuckold/hotwife.
All the subordinate activities (chastity, clean-up, etc.) are all there to demonstrate and gain acceptance in a submissive role. In basic mammalian psychology it is to remove the perceived male competition and to allow the 'man' to remain within the pack as a non-reproducing non-threat to the alpha males.
I'm a dominant male and for me it's about feeling more attracted to and aroused by my wife when I feel like there is the potential for her to be promiscuous or just knowing other men probably want to fuck her. I guess the potential for competition sparks renewed interest.
I started to become aware of my feelings around this in my 20s after I broke up with a girl I'd dated through HS and College, where I was her first and only partner. As I started dating again, it was hard for me to accept that pretty much every girl in her 20s had slept with multiple people. I dated one girl for a while and she wanted to be exclusive but, after just leaving such a long relationship, I wasn't ready to commit to one person so soon. So we just casually dated and at some point, she revealed that she was going on a date with someone else. I told myself I didn't care, because I knew I didn't really want to be with her long-term but I was very anxious while she was out and after she told me they'd had sex. I felt sick, jealous and, while she expected me to be mad, I instead wanted her to come over. Somehow I just felt like I needed to have sex with her, to make her mine again...
Anyway, she was kind of crazy and I probably would have moved on sooner but somehow I found an irresistible allure to continue fucking her even as she dated this other guy. I just really got off (literally) on sending her back with a worn out, cum-filled pussy and it turned me on that she was such a slut. They actually got married eventually, so I'm assuming he is probably into some form of wife-sharing now haha.
This and a later experience sort of set me on the path to eventually watching DP porn, which led into cuckold porn. I've never been into the humiliation, for me it's all about the woman being a "slut" and how hot I find that.