Why can't gastroenterologists come up with a test that requires less prep than the colonoscopy? It's backward?

The prep for a colonoscopy is egregious. Why can't doctors come up with a blood test similar to the PSA for colon cancer? There has to be a better way than to have to go through a prep where you literally have a 24 hour waterfall coming out of you right until the very second you finally are given the colonoscopy itself. Even the virtual colonoscopy requires the waterfall prep. Why haven't they been able to perfect the pill camera that you swallow that does the colonoscopy without any prep needed by taking pictures in your large intestine? It's criminal that they've made the 24 hour colon regurgitation the only way to do this procedure. It's a method that's at least 60 years old and has never been refined. It's a disgrace beyond belief and unbelievably degrading.