Why doesn’t the iPod Devices have a stop (■) button?
Because it is redundant. There is nothing you can accomplish with a stop button that can't already be done using the pause, menu, next track, and/or previous track buttons.
This is not the case with media players that are physically interacting with their storage, such as VCR's or DVD players. According to ecoustics.com [1]:
On a VHS machine, pausing the tape kept the same segment of tape rubbing against the playback drum, which if done for a long enough time could wear that spot in the tape. This could cause any number of picture and sound hiccups, or worse, cause the tape to break.
With a DVD, there's little mechanical difference between pause and stop unless you keep it paused for more than a few minutes, after which a stopped DVD motor will spin down but a paused one will continue to run [1].
[1] http://www.ecoustics.com/
See Questions On Quora