You're right that it would be ideal to simply wash the dishes before they accumulate, but I often find myself in situations where I don't want to do dishes before and after I cook. Moving the tub takes 5 seconds, washing the accumulated dishes might take 5 minutes, and if all you wanna do is rinse some berries and make oatmeal before you run out the door taking 5 minutes to do dishes might not be on the table.

Ultimately the dish tub and keeping the sink clear is a strategy I learned to avoid domestic blockers. Regardless of what everyone else in the house is doing, I need to be able to use the sink without doing a bunch of extraneous labor first. And getting mad at them for being lazy or messy or whatever might feel good but it doesn't solve my problem. There are edge benefits like the fact that I never find accidental mold in my sink, which is nice from a hygiene perspective, but mostly it's that I want to be able to use the damn sink when I want to use the damn sink.