Cutting out one of the most jolly and carefree Tolkien characters? Some fan. A 20 minute scene would've probably been fine, especially since he felt the need to "flesh out" the Hobbit "trilogy" with a bunch of nonsense that isn't even in Tolkien (Tauriel, white orc, etc).
If Tom had been included, the 1st LOTR movie wouldn't have sold as many tickets and the trilogy might not have been finished. Many people aren't LOTR fans, so the movies have to appeal to everyone. A 20 minute scene of Tom would've bogged the film down and confused many. A film has to make $, let's not forget.