Because it doesn't really mean anything. the "presenter" is not even a producer. It means that someone (whose name has some kind of value) saw the script or film and liked it enough to simply "lend their name" to help sell it.
Many times it is friends or family, or friends of the family who happen to be famous.
Example: Terry Gilliam presents DELICATESSEN (which is how it was released). Gilliam saw the film and loved it - so he told the directors they could use his name to help the film.
Although, DELICATESSEN is the exception to the rule- it is a great movie.
But how many "Wes Craven Presents", "Eli Roth presents", "Quentin Tarantino presents" - all those movies stink....
and of course - my favorite- movies that are presented by OTHER movies!
"American Pie Presents", "Fast and Furious presents: Hobbes and Shaw".....