This is sort of half-assedly in reponse to SnowdropExplodes's comment on this post at Figleaf's. Which was too incoherent to post as a comment. And probably more explicit than my run of the mill post, but hey, it happens.
This keys heavily into a theme that I've heard mentioned by submissives, especially women submissives, about the key source of pleasure (I've been told several times by subs that their preferred form of sex is fellatio, because "there's no direct pleasure for me; it's all about him").
I only like oral sex -- giving or receiving -- in a d/s context. I have occasionally poked at this a bit to try to figure out why this is, and I got nothing; the only clear notion I have is something about service sexuality, but that doesn't really explain why I don't fancy being the recipient either.
The thing I find most interesting, personally, about service sexuality stuff is the way it functions for me as very intense foreplay. The intense awareness focused on my partner's reactions ramps me up in a way that only active teasing can do otherwise; it frequently parses as a form of teasing.
"You're teasing me."
"You're still teasing me..."
"We both know what you want. You don't really want me to take the edge off, do you?"
I have a penetration fetish, in that sort of semi-technical sense; I am as a general rule not satisfied by sexual activity that does not include (typically PIV) penetration at some point, no matter how many orgasms I have (though I have done some experimentation to discover other potential means of achieving satisfaction). I find orgasms that come about from other activities notably more satisfying when they come immediately following penetration than when they come before, even if the same actions are taken. And so on.
In a d/s context as a submissive, I frequently wind up framing penetrative sex as a reward for service, sexual and otherwise. I certainly do non-sexual service stuff (and had a running joke for a long time that the anti-BDSM ideologues probably would be confused by the amount of carpentry involved in my kink), but if one removes the completeness-of-relationship-arc stuff that I talked about my linked post there, there's this core thread of sexualisation. Not in a transactional "If I do this, I will get kinky sex out of it", but a link forged between the task and the satisfaction-reward. And sometimes this is straightforward -- the "my assistance with this carpentry task cuts down the time required to complete it from three hours to an hour fifteen" sorts of things make for a lot more time to contemplate kinky sex -- and other times it's a lot more abstract. But still present.
And I can get into some interesting headspaces with sequences of service tasks, especially if some of them are sexual, that don't wind up including my personal reset button. Because that thread of sexualisation is there, and because some of our favorite things to set me to doing are sexual, it's a constant, complicated flow of foreplay. Sometimes the feelings are quiescent for a bit, and that tends to dull them out over time, but they can be let go for a while and then re-invoked with a new task, a reminder, a bit more active teasing, extending this foreplay over the course of days.
(Tangentially: When I frame it like this, I can understand orgasm control kink as potentially doing something similar when dealing with someone who's orgasm-oriented in the way that I'm penetration-oriented.)
It's something to do when there isn't time to fuck ....