It's surprisingly useful for T1s when we're assessing how far in advance to inject ahead of a meal.
If an item is, say, 30g carbs, of which 25g is sugars, that'll absorb very quickly, so we may be inclined to inject quite far in advance of the meal to give the insulin more time to get to work, so our bg is already on a downwards trend before the "fast" sugar hits gets quickly into stream.
Whereas, if it is 30g of which only 4g is sugar, that would indicate a more slowly absorbing food as the majority of it will be longer chain carbs which take time to breakdown and absorb, and in that situation we absolutely don't want the insulin activity peaking too early, so we will tail back the pre-injection time substantially to avoid a hard drop.
It's broadly related to the idea of GI, and makes a surprising difference in matching insulin timing to food absorption when taken into account.