On a forum, someone mentioned a podcast where the topic was cuckolds that go months, years or even decades without being allowed "normal" sexual intercourse. For obvious reasons, this baffles some people. One guy asked why, if as these women stated they loved their husbands, they denied said husbands this sort of "physical intimacy".
"Physical intimacy" does not have to equate to coitus, sexual penetration and/or ejaculation...and love may or may not have anything to do with sex. I could be physically intimate with someone I just met, and not even like them, much less love them.
Some male submisives see serving as their goal in life. Some may see denial, sacrifice and suffering as part of that...of which blue balls and that related discomfort is just one more aspect of their lot in life. One could be a eunuch and still be a sexual submissive, or a slave, with no hope of ever having the sort of "physical intimacy" of the type that the OP alluded to. Its a big world...and it takes all kinds to fill it. :)