Let them be. We become a nuisance doing that. Because people do not have the luxury of space to use, they don't live where that is ideal or they want the binaural nature of headphones and IEMs.
I have speakers and IEMs and they both serve their purposes. I didn't have the space for speakers so I didn't get any till last year when I moved into my new space. So let people be. Only thing they're truly missing out on is the psychoacoustic phenomenon of staging in front of them. But they'd trade that for no room issues which is more than 50% of what to look out for when using speakers