I'm not sure if that's necessarily true. As part of a workup for chronic GI symptoms that are nonresponsive to standard therapy, I can see some causes that might only be clearly evident with direct visualization. Strictures, HPylori sampling / ulcers, gastroesophagitis, malignancies, inflammatory bowel typically require endoscopy. Point remains though, this is for patients who have undergone reasonable workup in a step wise fashion, usually with lifestyle changes and medications beforehand.