If you live in an economy where these are uncommon, travelling to one where they are common and especially the equivalent for shower control in hotels.. is a logistical nightmare.

Its the eigenvalue of taps. It's hot, or it's not, and which orifice it's coming out of is completely unclear as well as which motion causes more, or less of water and heat.

Left and right for hot and cold, up and down for more and less flow. Very intuitive.

It sems these days shower valves have all been enshittified to have exactly one dimension, which proceeds from "off" to "small trickle of cold water", then "slow flow of warm water", and finally "slow flow of barely hot water".