Because, and I know this is bizarre, they haven't been trained to actually fix the problem. All of their training is aimed at them performing the Standard of Care for their specialty.

For digestion, the Standard of Care says:

• patients have to eat high carb, low fat, and lots of fiber
• the way to treat any issue is test and prescribe
• if patients don't improve, it's not your fault

This is not so bad for a serious condition, which is usually detected and has some reasoning behind it. But the run-up to the serious condition? They are not trained to detect and avoid that.

So, they don't.