In retrospect, it's easy to say that the deleted scenes should have been included. But you have to remember that FFC had a lot of problems with this movie, and Paramount didn't want the flick to be that long. FFC had cut the film down to 2:55, but the studio wanted him to trim it down to 2:20. FFC's contract called for a cut shorter than 2:30, and if he went over that then Paramount was going to cut it for him. Eventually they relented, and they put it back at 2:55. But there's no way that they would have allowed another 45 minutes on top of that. Remember, they had no idea the movie would be this popular.

If you take a movie like Harry Potter, the movie studios were certain that it was going to be a hit, regardless of how long it was. So they didn't really cut anything out of the book, and they made one long-ass movie. But there were no such assurances when it came to The Godfather.