Because items allow you to play the game at whatever level of difficulty you want to. If you're one of the people who wants a crazy challenge, the stages are there for you. If you don't want to deal with any of that bullshit and just get your stones, that's what items are there for. I don't see any good reason more intensely difficult stages like these shouldn't exist for people who get a kick out of that kind of thing. If they're not what you want, there are easier stages that probably fall more in line with what you're looking for.