Movies, like books, are primarily works of CULTURE AND ART AND STORYTELLING - and neither of those can ultimately belong to one person or a group of persons any more than the works of Shakespeare or the Bible or the Greek myths do.
That's because the Greek poets, the apostles, and William Shakespeare died more than 70 years ago. For example, translations of the Bible into modern language are still copyrighted.
Someone can own a block of wood with a Mona Lisa painted on it - but no one can own Mona Lisa no more than anyone can own the letter 'A'.
As you go on to explain, someone could own the exclusive right to make more blocks of wood with a Mona Lisa painted on it. Had current law applied then, this exclusive right would have expired at the end of 1589.
So we have laws to try to make sure that at least some people pay for what they willingly experience.
And pay for what they not-so-willingly experience. The music publishers get a cut of the revenue of grocery stores that play music, for example.
people will demand more than just a "recording of two people fucking for money".
But does that explain pseudo-amateur porn films such as 1 Night in Paris? What was Ms. Hilton really famous for before that film?