Text files just aren't the same. I'd rather be able to see the pictures that go along with the story of the game. Plus pictures make the manuals more fun. Just think of the Super Mario 2 manual. It was eye candy.
Instruction manuals are for wimps.
I've never been too fond of manuals that came with games, and thus don't miss them very much. Still, is Super Mario Bros. really the same without the manual telling you that you can impress your friends and parents by jumping on three enemies in a row, thus earning - 700 yes 700 points. It's almost as fun as forming a military coup to overthrow the oppressive government and replace it with a totalitarian regime. All hail the righteous banana. That about sums it all up.