Warp zones allow players to see more of the game. If you were a kid playing SMB, and was only allowed 30 minutes a day to play a game, you would probably never get to experience any of the later levels without the warp feature.

Not everyone games the same way. For many people, cheats add to the experience, they don't detract from it.

Sometimes I want to listen to an album straight through; sometimes I want to skip to specific tracks. Either way, it's the same amount of experiencing the music/game; it's just a shift in what parts of the work you're giving your focus.

I agree with this philosophy for most games. I tend to play through them once and not revisit them once completed, so I try to experience as much of the game as possible on that first playthrough. (Up to a point anyway. Sometimes certain content e.g. gathering collectibles becomes boring or tedious. And sometimes I'm enjoying the content just fine, but feel the need to hurry up and finish the game so I can move on with my life.)

Needless to say, SMB isn't most games. It's the type of game you play again and again. And it does not natively include any game save or password system. The warp zones transform it from an hours-long marathon to something you can play through during an episode of your least-favorite Saturday cartoon.