As AZYooper mentions, plenty of evidence shows no value (to the patient) of monitoring UC disease activity by scopes.
Setting aside profit motive, many docs just aren't very good clinicians and rely on technology rather than their own intelligence or experience in part because it's so easy to do. With UC, I haven't gotten the best care from these types of docs. And no one would respond positively to another professional operating in this manner.
For an imprecise analogy, docs don't require a nuclear stress test every time a patient with high blood pressure isn't responding to medication or needs to switch medication. They add or switch medications.
Even the cancer risk needs to be taken with a grain of salt. The average person has a 3-4% chance of getting colon cancer. After 10 years of UC, that risk increases by 25%, which is to say a 4-5% chance of having colon cancer, not a whole lot more than the general population.
At 20 years or more, the risk does go, sometimes quite a bit, which is why many protocols recommend prophylactic colectomy rather than continued colonoscopic surveillance which recent research indicates isn't as effective as previously thought for catching the early cancer. (Which is not to mention that any surveillance c-scope for UC patients should include something like 30+ biopsies to be considered effective.)
C-scopes have their limitations.