Cups, teaspoons, and tablespoons in this context are standardized units of measure. It is very common to find at least one set of measuring cups and spoons in a US kitchen. Scales are uncommon.

I use both. For flour, scales are far, far superior. For sugar, it does not really seem to matter. For small amounts, I suspect my tea/tablespoons might be more accurate than my scale…

Not that accuracy matters that much in a recipe using eggs. Chickens aren’t necessarily known for precision.