First of all, sexlessness rates are probably also linked to lots of other factors, like simply the availability of p**rn. I also think that simply the availability of the internet may be important. In our time, a person can spend a large portion of their time online, and never get bored. This reduces how much time people spend socializing, and so forth. Another important factor probably is that people's lifestyles have changed, and people take far longer to settle down.
The decline in sex happened both among men and among women, though it has been more significant among men. So we need a model that explains why both sexes are having less sex.
Does your model explain at least part of why men's sex rates have declined more than women's? Quite plausibly, but it still seems like a small part of the overall phenomenon.
And also, I maintain that in the long run, almost everyone in our society desires a long-term relationship. Sex-starvation of unattractive males due to the hookup-culture, to the extent that the phenomenon exists, probably shouldn't be a problem in the long run.
Maybe it can give you a relatively sexless youth, but in the long run, I maintain that most ablebodied and ableminded people who desire to be paired and have realistic standards will be paired.