Why do iPhones let you take pictures when it's locked?

I have an iPhone 4 and i noticed that when it's locked it still allows you to take pictures. Why is that?

Simple quick access to your camera tht way you don't have to unlock it just to take a picture

So people can screenshot their home screen… Its the same idiocrocy that makes girls take pictures in bathrooms… LMFAO

You can change that in the settings(general).It will ask u if you want it to be able to or not.

Quick access… Thats the way it should be.