Perhaps it's because his goals are different from yours?
"We" don't need to worry about anything, and what's important to you isn't necessarily important to him or me. Furthermore, there's nothing that says someone with type 1 (or any diabetic for that matter) needs to follow a low-carb diet. That is a lifestyle choice not a requirement.
Calories aren't as important when you're 40+ pounds overweight or have 20%+ body fat (I'm not suggesting you're either of those), but they become EXTREMELY important when you have a lot less to lose.
Furthermore, while carbs and fat may be metabolized differently by our bodies, it is fat IN THE ABSENCE of carbohydrates that is the important variable. A high fat diet combined with even a moderate carb intake can lead to significant weight gain.