It would make the game less challenging, and that's because exploration is part of the game. And you don't have to collect everything in the level to proceed.
Also, the requirement makes the game more fun, because it is a big clue to the player that there are other hidden areas to discover, with more hostages to rescue, giant peanuts, I even found an Xbox code that cashed out for $50! (Okay, I made the last one up.)
Everybody needs to check their expectations. "Oh, so I'm an elephant and I can break through things... that means this game is about nothing but smashing through everything as fast as possible!" The same kind of misconceptions have certainly plagued the Sonic series. Just because you bought a game doesn't mean you've earned the right to effortlessly see the ending. You've got to learn the game and beat the game! Welcome to old school platforming! (Although this is much, much easier than old school platformers, honestly.)