To control when/how it turns on and off, show status on a display, ... It being programmable is a bit of a gimmick for most, but the usual caveat applies: You might not need it, but if you want/need some customization it's very nice if your hardware actually allows you to add custom firmware. (E.g. for the TS100 there were some features that as far as I know first featured in custom firmwares, e.g. flipped display for left-handed users)