IMO perceptual uniformity isn't even necessarily desirable in all (or even most) cases.
The only time I think it's really necessary is making color palettes for data visualizations.
Otherwise, if you're e.g. designing a color palette for a webpage, you probably do want some variation in perceived brightness. Heck, I could think of plenty of valid data visualization scenarios where you'd want this.
I want to be able to have variation in perceived brightness, but not as a side effect while browsing for a hue. I doubt most designers would argue otherwise.
Compare it to waiting for a compiler: Sure, you can use the time off to stretch and take a sip of tea but there would be no serious opposition to compilers working at double speed tomorrow. It's simply better to not have to wait (all else being equal). But it's something you accepted and you deal with it, so wait you will.
The current color pickers are an annoyance that we have lived with since, well, always, but an annoyance nonetheless. Happy to adopt these pickers if they gain adoption. OKHSL and OKHSV look spiffy.
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.
I worked on software that had the ability to change the hue of an object. If you had a bright blue car and wanted it to be yellow, changing the hue to yellow worked perfectly. Then the perceptually correct zealots took over and mandated that all color manipulations would take place in the Lab color space. Now the intense blue 0,0,255 didn't turn into an intense yellow 255,255,0, it turned into what was considered a yellow of the same lightness - 31,31,0. This was too dark to be useful to anybody, and there was no way to compensate. Worse yet it wasn't even correct, because the lightness isn't accurate for intense saturated colors - if you look at 0,0,255 and 31,31,0 side by side you'll see what I mean, they're not even close to the same perceptual lightness.
The only time I think it's really necessary is making color palettes for data visualizations.
Otherwise, if you're e.g. designing a color palette for a webpage, you probably do want some variation in perceived brightness. Heck, I could think of plenty of valid data visualization scenarios where you'd want this.