Yes, 20 years ago there were physical manuals in physical games. That was 20 years ago. I'm pretty sure that Larian has switched to digital versions only because of the greatly diminished returns from making physical copies. It's just not profitable enough publishing physical copies for Larian.
Any printed manuals would probably only be for a special collector's edition, or in physical console versions of the game, and even then, the player's handbook is over 300 large pages. Even if that was cut down to, let's say, 150 by not including anything past Level 10, and trimming out flavor and artwork I really can't see a physical manual that big.
