Why are gastro-enterologists so quick to issue an IBS diagnosis when in fact you have other problems?

I just went to a gastroenterologist about digestive problems, thinking I had IBS. The doctor said that IBS is a "diagnosis of exclusion," meaning you're supposed to exclude EVERY OTHER POSSIBLE AILMENT before diagnosing IBS. Therefore, it's obviously a difficult process to cut through all other possibilities, why some doctors (or should I say, lazy doctors) just shoot to IBS right away, mostly because IBS causes so many symptoms...so it's an easy things for doctors to just say you have without doing all the tests they're supposed to. I would go to another gastroenterologist who specializes in what you have, to make sure you're in good hands. Good luck and good health!