Although with things like spices, there’s no point in measuring them anyway. Spices are almost always added to taste, so it’s easier to think in terms of ‘x hand movements with the container’.
And yes, I have actually weighed 8oz of water. Well, not specifically 8oz, but I’ve certainly weighed out water to +- a couple grams for a recipe. If a recipe is specific about contents, why would I not measure it out?
I’ll nitpick that said definition is also arbitrary. Why is it 1l of water at sea level, and not molecular weight of the water? And why a Liter anyway.
Even metric units like time are somewhat arbitrary. Why is a second based on caesium frequency, and not some other element?