why can't we count breads? but we can say 1bread ,2bread ?

we can count breads but we can not count a peace of bread.

we cannot usually say “two breads” because “bread” is uncountable. So, if we want to specify a quantity of bread we use a measure word such as “loaf” or “slice” in a structure like “two loaves of bread” or “two slices of bread”.