Long-term studies like the UK Prospective Diabetes Study (UKPDS) and the Diabetes control and complications trial (DCCT) showed that intensive insulinotherapy achieved blood glucose levels closer to non-diabetic people and that this was associated with reduced frequency and severity of blood vessel damage.
This evidence convinced most physicians who specialize in diabetes care that an important goal of treatment is to make the biochemical profile of the diabetic patient (blood lipids, HbA1c, etc.) as close to the values of non-diabetic people as possible.