Sex is the culmination of love. The two have to go together.
Now of course, you can have sex without love, which as a lot of escortcels here have reported, doesn't feel all that great (or not as great as they had hoped). You can also have love without sex but i think that's more of a spiritual kind of thing, a practice often found in some religions.
One thing i do not believe in the slightest is that people want sex because they want children. Not to say that having children isn't an attractive prospect for some people, but i firmly believe that sexuality exists for its own sake, and i also believe it is a kind of "metaphysical" experience which is why it is so difficult to be happy without it.
This was argued by Evola in his "Metaphysics of Sex", a book which frankly altered my understanding of sexuality forever and also provides an explanation for why sexuality is so important for most people and why inceldom is such an ordeal. I won't go into details since the book talks about a million of different things, all connected with esoteric or metaphysical concepts and practices, but the gist of the problem is the following. Material existence is essentially limited, "relative" and transient. Nothing in this world is actually capable of proving an experience that can liberate a person from the crushing realization of his own relative condition EXCEPT for two things, spiritual realization, and "sexuality" (but only from an higher point of view, which we erroneously refer to as "love", even though the experience in question as nothing to do with mere sentiment).
The reason being an incel causes so much suffering is that you are basically imprisoned into an existential cul-de-sac. Everything is a "cope" because only metaphysical experiences can provide liberation from the oppressing condition of being forced to exist in a state of pure relativity. What human beings experience during coitus is a type of existential respite from the torturing limitations of ones own finite ego, however briefly, and it is the only means normal people have available to them, the path of higher spiritual realization being limited to a select few even in traditional societies, and we no longer live in such societies so there's also that problem that one has to deal with (monkcelling was legit because of this, btw, because it fulfilled the need for the metaphysical which nullified sexual desire altogether).
Human existence is not about survival, it is not about procreation, it is not about hedonism. It is about meaning, and meaning is found only in metaphysical experiences. All those normies who scoff at incels would be behaving exactly like incels do if they were to be flung in the same predicament. Inceldom is literally the existential equivalent to life in prison.