Why do people do crunches i mean they really dont do anything for you why dont they just do normal situps?

they are easier because sit-ups hurt your back, but crunches can do a lot if you do them correctly

Crunches will do for you what a normal sit up will and i understand what you mean, however the crunch is a much stricter movement whereas in a sit up it is possible to recruit hip flexor muscles and also gain momentum with the arms which makes it easier to do. It also puts less stress on the lower back to crunch rather than sit ups.

So for those with poor technique, bad backs or are inclined to cheat, the crunch is better, but for others it is just the same as a sit up

sorry to say but sit ups crush your pelvic floor, eventually you wont be able to control your bladder and when you pee! its not a very well known fact but look up hawthorne football club on google, it happened to all of the players and they peed at the most inconvienient of times. yeah- steer clear of the sit ups, i thikn thats why crunches are more promoted =)

best of luck