With a touchscreen you have the whole time it's on the screen to touch it (if we say the list is ten items long, and it's moving at 5 items per second, that's 2 seconds, not long but manageable) while with the select button, you have only the period it's highlighted (One fifth of a second in the previously mentioned example).
Definitely significantly harder to use without a touchscreen. Now, a tap could cause the screen to stop scrolling without selecting anything, after which you'd need to move it a few entries to the right one. But overall it still just doesn't make too much sense functionally on anything but a touchscreen.