> my general impression is that doctors live under this illusion that patients will somehow succeed in making lifestyle changes
> Also, they prefer to try medications like glucophage before they resort to insulin.
A couple of points: 1- the targets set by associations like the ADA actually assume the patients won't be able to make significant lifestyle changes; for example the ADA A1C targets are higher than for healthy patients. The diet changes they preach are not that radical, e.g. cake is bad for you but you can have a really tiny slice and offset it by not eating bread. This belief isn't that unreasonable; FDA requires that medical labeling be targeted at a 5th grade reading level.
2 - And glucophage is much easier for patients to manage than insulin both in dosing regime and simply caring for the drug.
3 - Finally the insurance companies' actuaries have figured out that maintenance therapy of this nature has the best cost/outcome ratio.
To that last point: I had "adult onset type 1" due to an autoimmune condition. The endocrinologist I was sent to was only interested in maintenance therapy and not at all in looking for root cause, even though I presented with a body fat of about 14%. She finally admitted that even if she did look into it the insurance companies would hassle her for going off the reservation without a good excuse.
But my no-insurance primary doctor and I and a rheumatologist were able to dig into root cause and now I am "cured" (of diabetes at least) thanks to treating the underlying condition (note: this is glossing over a lengthy period of unpleasant work). Which is actually cheaper for the insurance companies, but honestly how many patients have the training to be able to be involved in their care to this degree?