Because it’s way more precise than pouring liquids into a beaker (which can be off by 10%), much easier to judge than bending down to judge a level, and since with water 1 ml == 1g (yeah, metric system helps…) fairly easy to calculate. All other liquids commonly used are close enough.
Also what the fuck is 3 cups of flour/rice/salad (?!) even supposed to mean. Loosely packed? Compressed?
I don’t know if it’s an advantage, but I’ve seen one lately, and it was fucking loud.
Like eeeeeeeEEEEEEEEEEEEEEEEeeeeee loud.