You obviously never used one. It gave you full, immediate control over how fast you scrolled, which buttons could never do. It enabled you to immediately change direction without lifting your finger. You could start by placing your finger anywhere on the wheel, which made it easy to use in the dark, and moving your finger from the wheel to the button in the center was just as easy.
It was, and still is, the best interface I've ever used for navigating through large, grouped lists.
You could also adjust the volume through your pants, at least with some versions. It was just sensitive enough that I could do this with jeans without having to stick my hand in my pocket. Honestly this was one of my favorite features, at least until the headphone remotes.
That is exactly why Apple cleaned up and previous players didn't.
From a technical point, that is correct. From a usability point, it isn't - because it took a previously digital control (button pressed or not) and made it feel analog (just turn the wheel).
And it's much easier to precisely navigate over large distances with an analog(-feeling) control.
Of course it wasn't only the wheel that made a difference, but it was the mindset behind it: Take things that to most engineers are functionally equivalent and choose the one that makes it easier for the user. Or find something that makes it easier for the user.
That is a lesson that many of the products of our industry are still missing. What matters is not only functionality, but how easily and intuitively I as a user can access that functionality.
Not only still missing, but largely extinct. Analog displays had two brightness/contrast dials (or knobs? can't find a word), and you just rotated it until done. Now I have to use crappy OSD menu with 4 plus/minus/up/down/enter/exit/auto/mode/etc dynamic buttons each time I need to adjust these. Some manufacturers' ui designers are even so dumb that put unobvious logic into it like when you first press minus, it adjusts contrast, and when plus, it is brightness. HOW could that happen to the industry?
Because it was tactile, and allowed for you to spin at higher and lower speeds. Good luck pressing a button with any velocity at all, and I've never seen the "press and hold for higher speeds" thing done half as well. Not to mention that it completely lacks in terms of feedback.
The smartest thing they did with the click wheel after the wheel itself was the little clicking noise they played as you spun it. It made it feel mechanical, and gave you immediate feedback about how fast you were going.
