stevenasty said: It seems that only men want to be cuck. . .
I think there is a common misperception that the OP was referring to a cuckold fetish. While a cuck fetish does involve a man seeing another guy doing his partner, the fetish is all about disempowerment for the guy doing the watching. It is a humiliation thing, full of rejection and catering to feelings of inadequacy that are celebrated. And there is a whole racist thing happening that plays to some of the most destructive Civil War - era stereotypes there could be.
That's why I react so negatively to cuck fetishes and to cuck videos. They make my skin crawl because of the disrespect they are intended to show. No thank you - for me it's almost like a scat thing. Not happening!
I think this thread is about something else entirely. Take away the cuck fetish, take away the abuse, manipulation and humiliation, and replace it with a committed couple and a third friend, fuck buddy, lucky guy, what have you. For me this "fetish" if that's what it is, depends on mutual attraction, mutual respect and appreciation, and is a way for the guy to enhance his partner's pleasure.
He will be feeling perfectly "adequate" - in fact, much more than adequate because he has the confidence to open up his sexual relationship to another man (with whom conventional wisdom suggests he should be in competition). So he is a confident sexual partner. His wife, sig/other is equally confident in her relationship with him, as she feels free to indulge in extreme passion with another, freely and without angst. The mutual attraction between the three brings with it a trust that no harm or disrespect of the relationship is going to happen.
I see this from a male (MMF) perspective, but I see no reason why it can't be equally powerful for a MFF, MMM or FFF threesome. For me it's about primal lust, passion and freedom to let go without a hint of reserve. That requires confidence, trust and mutual respect.
Imagine such a feeling!