Hmm...
From what I studied (Psych major in college and for fun), rape is mainly about power; whether to establish it or taking it to feel powerful.
That's why the All-American star quarterback would have no problem taking sex from a woman with booze and coercion (word to Mettenburg and Rothlesburger

)...
To the cat in the dark alley would drag someone to the ground and take sex at knifepoint...
To the lonely dude who'd roofie is female next door neighbor just to fool around...
To the dude in prison that uses prison rape as a form of intimidation...
To even the girl that got her best male friend shythoused (while she stayed relatively sober) so she could have sex with him...
Power (whether to establish one's own or taken by force) plays a HUGE role in the act of rape.
If it was just "about getting a nut," they'd hire a prostitute or masturbate; which is a whole lot easier and less likely to get jail time from.