[atoav]

Another application that might not be as rare as one would like to think is color-interpolation. Interpolating colors in a way that doesn't make them perceptually brighter or darker is hard.

As someone who deals with color pickers a lot, it is just nice to have multiple options. Sometimes I just wanna punch in a hex number, sometimes I want a SV+H square, sometimes HS+V works better, etc.

I see value in having a color picker that allows you to pick colors without changing brightness. E.g. imagine you let users pick colors that should work on a background that you designed. giving them a color wheel that stays perceptually at the same brightness has value here, because no matter which color they choose the brightness-contrast on your background will work.