Added sugar is not necessary for yeast. The yeast is breaking down and using the carbs naturally present in wheat. The simplest breads, like french baguettes, are only made with flour, water, salt and yeast. Sugar is added to many commercial breads because it can make production easier and more consistent and sell more to consumers, but it's not added because it's necessary.

It's less than one flat teaspoon per loaf, and most of that is metabolised by the yeast. You can do without it, but it takes much longer to rise.

Ok, of the carbs in white bread here there is 0.6% sugar. That's completely negligible and now what I'm referring to at all. I am talking about added sugar where it will be 10-20% of the carbs in the white "bread" (I consider that pastry :D).

The yeast metabolises that sugar.

I think people are talking about adding sugar for taste, beyond what the yeast can metabolise, which is common in US food culture but not generally elsewhere.

Check out Czech bread. Completely sugarless.