I think people are failing to realise that for some people sex is not really that important .
My libido is much lower than dh's, it has always been low in long-term relationships regardless of how much I 'fancy' my partner. I do make the effort even if I don't feel like it as I know how important it is for dh and generally most of the time I enjoy it, have an orgasm or two etc.
Like a lot of couples our sex life consists of a mix of wilder sessions. the occasional use of toys, some more intimate gentle sessions and some ' hey that OK but nothing special' sessions.
I pretty much always enjoy the sex (sometimes a great deal) but tbh after the inital first thrill of meeting someone I personally don't find sex a particularly good way to feel close to someone on a regular basis.
Some sessions do result in me feeling closer to dh and more loved but many are just either very good fun (even wild) or Ok (depending on the mood) but do not result in me feeling particularly closer to dh.
This means that it can be difficult to summon the enthusiasm for sex when for me the pay off isn't always enough to warrant the effort.
I do appreciate that for dh though he does feel closer to me after sex so I often agree even if I'm not feeling like it because I love him and because I know it I usually enjoy it once we start.
It is just the wanting and to do it in the first place that is the issue for me.