Are kitchen scales accurate enough for such tiny measurements? 1 teaspoon is 5ml, so if your scale only has 1g of precision you're looking at up to a 10℅ variance (assuming you're measuring water), and that's assuming its accurate at that range. It gets worse when you need to deal with fractional teaspoons.

Yes, and there are lots of recipes that use mass rather than volumetric measurements. For solids, in fact, many sources prefer this because consistency of packing density and other user factors that effect consistency with volumetric measure are far worse than with mass measured with a kitchen scale.

The exception is usually butter, which is measured in grams (and conveniently indicated on the packaging).

I live in Europe and have always weighed exactly 100g on the scale, whether I was asked for 100 grams of butter, sugar or flour.