I’ve noticed that I often want to adjust the pen position: to replace the paper, to adjust the pen itself, add/remove weights (which I find very helpful with certain drawing implements), etc. Basically, I find I use the pen up/down and motors off to re-Z a lot, making a hard-wired button helpful. My studio is set up in such a way that my Axidraw isn’t very close, so I have to go back and forth. By no means a must-have but seemed like a useful mod.