You seem to think that "using all of the loaf" means "forcing larger portions onto children."

But the sandwich is the same size whether I make it with end pieces or not.

Not everyone has access to the abundance you're talking about, and that abundance isn't guaranteed to last forever. Food waste contributes to the overall demand for agriculture and its side effects, including carbon emissions, water usage, and destruction of natural habitats. I'm not going to pretend that the ends of the bread make that much of a difference, but an attitude of using what you need and not wasting things unnecessarily has many benefits.

Eating the end piece doesn't mean you have to overeat, just that you don't need as many loaves. The end pieces having a higher fiber content may even keep you full longer, leading to eating less through the rest of the day, helping you with your goal of consuming less total calories.

I don't suggest forcing kids to eat anything in particular, as long as the overall food picture is healthy. And if the kid wants to eat bread, they should have to eat the crust, including the occasional end piece.

Not all bread is created equal. Some breads are quite nutritious, and the crust tends to have more nutritional value than the rest of the bread.

LPT: Be honest with your kids and teach them responsibility. Even if they don't like the end piece as much, they should learn that it's right to eat it anyway.

Any measure of happiness or sadness is going to have inherent bias and error. It doesn't make the measurement bad or unuseful.

I know a couple people who get indigestion when they eat meat but not eggs or dairy, so they choose vegetarianism.

Some vegetarians also want to limit their environmental impact, but also realize that social eating is limiting and getting enough of certain nutrients is difficult if you're vegan, so their compromise is vegetarianism.