The Big Cheat in The Lord of the Rings that nobody talks about

Especially in The Lord of the Rings: The Return of the King (2003), but it is manifest in all three films;

Why is Frodo the main character leaving, while Sam is the one the audience is left to identify with in the last scene? It would probably been easier to stop the film earlier, so there must be some reason, aside from “Oh, but I want to film another series of shots!”.

The only even possibly valid assumption seems to be that Frodo is “too far out there”, too risky for “the audience” to identify with, so we’re left with the safe Sam at the closing scenes to establish a regular family life.

There is another, far more alienated, but probably academically acceptable answer:

The story of Frodo is too homoerotic; even at the end he still has only male friends, even while Sam goes off and gets married and has kids.

Then again, it seems to silly to blame homophobia on Hobbits, doesn’t it?