Diabetes is a condition where a lack of insulin leads to loss of control of blood sugar and death.
It is therefore assumed that the primary object of insulin is to control Blood sugar.
HOWEVER
if we did not have problems with type 1 diabetes then insulin would probably have been seen as an evolutionary hormone designed to drive glucose into lipogenesis and into fat cells for the winter. (What it actually does).
our understanding of the function of insulin in popular science is skewed by how it was first discovered.
Remember insulin has many different functions and these have quite an influence on both symptom and management of diabetes, and can suggest different strategies for T1 and T2. From my immediate need to learn this stuff three years ago my paraphrasing is
1) movement of glucose to muscles, when exercising, additional receptors are activated, in addition to other transport mechanisms to improve glucose transport rate. That's why exercising T1s with an amount of circulating insulin are at risk of hypos during exercise - they can't do the same as a normal person and reduce insulin production - I have to reduce my pump rate 3-4 hours ahead of time
2) fat storage hormone, stores excess glucose as fat
3) suppresses fat utilisation (preference for use of glucose as fuel when available)
Hence, to lose fat/use fat needs minimum insulin circulating, easy enough for me if a bit of a faff and requiring planning. For a T2, where they are insulin resistant, high circulating insulin lays down carbs as fat, prevents it being utilised and with the insulin resistance means those circulating carbs are not as easily utilised either. Hence T2 tends to be linked to obesity, but the question of cause vs effect s being rethought in some medical circles.
Also, with that premise in mind, a high carb diet, with those insulin spikes again logically contributes to obesity. So being able to efficiently burn fat = low insulin = low carb.