I personally have never understood that attitude. Dont get me wrong im not judging you. In my mind i just rather do something productive than idle on my phone, more so if there is even small change it will lead in to something better in the future and so far it has been paying off.

And from the employer side, if the shit hits the fan and there is layoffs, they will rather keep the dude that is effective and knows how to do things outside their job description, than the dude whose job has lots of downtime and they show bo enthuastism to doing other things.