After the DCCT, a large study on type 1 diabetics with good hypoglycemia awareness, with a very large portion with kidney disease, showed that frequent review and revision of insulin doses with an aim at normalizing glucose levels decreased risk of death as well as risk of kidney failure and progressing eye disease, public opinion swung strongly towards the idea that normalization of blood sugars was a good thing.
But in the following years, a number of large studies on type 2 diabetics showed pretty strongly that aiming for and even achieving lower A1cs wasn't associated with better outcomes. Those with lower A1cs had heart attacks and died at roughly the same rate as those with higher A1cs. One study (ACCORD) even stopped early because the people in the part of the study aiming for "better"- more normal- blood sugar control were dying faster.
Aiming for lower A1cs, in both type 1 and type 2 diabetes, has been shown to lower the risk of development of certain complications, most especially kidney disease. But the majority of diabetics- especially those who are not diagnosed at ages where kidney disease is at the highest risk of developing (dx roughly 10-45 years old) die of heart disease. And no study yet has shown a decrease in heart disease with intensification of blood glucose control.