Sliders belong in ballparks and bags of cheap burgers. They do not belong on most people’s audio gear:
When it comes to audio equipment, sliders were popular with some people and maybe they still are. They got some cachet when big mixing panels used in theaters and recording studios came out from behind their curtain. Oh, cool! thought I and a bunch of other people. They might be okay in their original applications, or where space is at a premium and you need to cram in a bunch of seldom used controls into a tiny patch of panel, but for everyday audio controls they suck.
You grab hold of a rotary control it is easy to tell how far you have turned it, even if the knob is on a radio mounted in the dashboard of car that is bouncing down a pothole filled road. Try adjusting a slider under those conditions and you can’t, not with any degree of precision. You can’t even adjust a slider accurately without being able to see it so you can tell how far it has move. Okay, maybe this is a personal problem. Maybe sliders don’t cause you any difficulty.
Not that much, really, but in automotive applications, they’re pretty much useless because you have to look at them, while you’re supposed to be looking at the road. Those newfangled touchscreens have much the same problem, magnified further if you started digging into the French fries before you got home with the burgers.
That said, the Big Receiver in the house — forty years old now — has ten sliders to run the equalizer. I think I set them once in 2003 when I moved in, and haven’t touched them since. The volume control is a proper knob. And in the car, where Bose has festooned the head unit with no fewer than thirteen buttons (not including Eject), the volume control is a proper knob.