Say you're standing in a high-traffic area, like the convergence of the main entrance to a building, the only entrance to a cafeteria and the entrance to the men's and women's restrooms. While standing there, you're talking on your cell phone - speakerphone-style.
How long would you yell into the phone, 'I CAN'T HEAR YOU! TALK LOUDER! THERE ARE A LOT OF PEOPLE AROUND!' before you'd use the phone the old-fashioned way?
Seriously, let me know, so I can tell the girl in the hall.