[siriaan]

In the physical world, sure, but there's no reason why a virtual linear slide could not be made endless

[squeaky-clean]

You'd have a discontinuity. A knob naturally rotates back to its start. A slider never does and would have to pacman-wrap itself back to the start.

There's no motion you could make that would infinitely increase without a break. A knob you can just move your cursor in a clockwise circle infinitely.