As I understand things, epinephrine is the hormone that produces the syptoms we associate with low blood sugar - tremours, pallor etc etc.
In my experience, we become less sensitive to the effects of this hormone if we habitually run low or have very tight control of our blood sugars. It sounds as if you probably have very tight control of your sugars?
I have kept my sugars in the range of 30 to 90 for years now which means I have no complications on one hand but no warning of hypos on the other! I've just changed from humulin to lantus to see whether that helps with the epinephrine sensitivity..... We'll see.
I'm very jealous of anyone who feels a hypo coming in the 60's. If only...