Why do some men submit?
For a complex array of reasons.
Because we are taught it's better to give than receive, and this applies to pleasure as well. Because if you love your partner, their pleasure should be more important than your own.
So we can learn how better to please our partners, both in bed, and in our daily lives. So they can teach us not only how to be a better lover, but also, to be a better companion, a better boyfriend, and a better human being.
And on that last thing, this should be why we should be picky about who we submit to. I want someone who is a righteous, intelligent, and moral person, so I can grow and be a better person by being with them. Not a swindler, scammer, bigot, or someone lacking in general empathy.
Because we admire strength, both physical, and strength of personality and of the mind.
Because the thought of someone else taking control and surrendering to them unconditionally is not only a huge sexual turn on for me, but it's an act of love.
These are my main reasons.
I very consciously avoided talking about kinks here. Yes, I obviously have them. But some people tend to get turned off by excessive wank fodder, so I will try to be "Good" and avoid posting about that stuff, from here on out. And, in my years I've found that any relationship based purely on kink cannot last anyway. After a while you crave the emotional and personal connection.