This is probably the primary reason why they don't want kids on any kind of LC diet.

Having them on LC means they need to stick to LC 100%. They can't deviate - they can't sneak a candy bar because they think if their parents don't know about it, that it won't matter.

It's already extremely difficult to adjust insulin for T1's because sometimes the pancreas of a T1 produces no insulin at all, sometimes it produces a little, sometimes it shoots out far more than needed... and sometimes goes through that roller coaster in a single day. Their blood sugar can be all over the place with no change in diet at all. Keeping them on a higher amount of carbs does serve a purpose there - and it's not to keep them on drugs, it's to give them enough blood sugar so that they don't suddenly drop down to 35 and die when their pancreas suddenly decides to shoot out way too much insulin. Their blood sugar is extremely erratic to begin with, and the insulin injection needs to be adjusted constantly to bring down blood sugar that's gone way too high, or give glucose tablets to a T1 child whose insulin has suddenly dropped dangerously low.

For T2's you're still talking about a child who is not fully developed physically, much less mentally and emotionally. So kids will be kids, and if they decide they're sick to death of not being able to have a candy bar or birthday cake, they will figure out a way to sneak that food because they think they can get away with it. Even if they understand the effect of carbs on their blood sugar and the need for sufficient insulin, a child's logic says they'll just give me more insulin if it goes too high.

I was about to say that you might be able to trust teens to keep tabs on their diets and their own blood sugars more carefully and be more committed to staying LC, but teens are such a wild card when it comes to rebellion, even when it comes to a health problem that could land them in the hospital with organ failure or result in death. Teen girls with T1 are a particularly dangerous combination - it doesn't take them long to figure out that they can eat anything they want and not gain weight as long as they don't use enough insulin to bring their blood sugar down.

But then when the kid ends up in the ER throwing ketones - as it says, it's difficult to tell if it's nutritional ketosis, or if they're in ketoacidosis - and the kid is not likely to admit that they went on a carb binge, because the immature mind just doesn't want to get in trouble for cheating on his diet, even if it kills him.

I worked with a lady back in the 70's who was a diabetic. I suspect she was a T1 because she was very thin, despite almost always having a donut or candy on a break. She told me that the only time she was careful about what she ate was for a few days before she had a Dr appointment. She was well into her 40's or older, and had been getting away with this tactic for decades. A1C tests were not in regular clinical use until a few years after that, so she figured that what her Dr didn't know wouldn't hurt him. It was probably hurting her, but not to the point that she cared.

If you can't trust mature adult diabetics to avoid excess carbs, how can you trust a child to do so?