For the umpteenth time: not wanting to have a sexual relationship is not new, it's not unheard of, it's not weird, and it's just one aspect of a whole human being.
Where I would agree with you is that young teenagers are expected to have heterosexual sex, often before they have worked out if they are gay or lesbian, or even if they want to have sex at all.
Underage sex has become normalised, I've heard parents saying 'Oh they're going to be doing it anyway' while allowing their 14 and 15-year olds have sex with their boy/girlfriends in their own homes.
However I also know of parents struggling against this tide of normalisation.
So it would be a great idea if young teenagers were given the time to decide whether or not they want to have sex and who with.