Why limit what you say to just cellphones?
What about vehicle traffic (never heard of road rage when I was growing up), waiting in lines, people who do not open or even hold doors for others, males do not give up their seats to ladies, people talk over others, I don't hear many who say "please" or "thank you", people answer phone when you are talking to them in person or on phone (I believe use of call waiting to be rude - that is what voicemail is for).
I could go on and on and on...
I was brought up to be courteous towards others, showing manners and simple common courtesies as a way of life.
If I didn't, whatever happened to me (say, at school) wasn't anywhere near what I was gonna get when I got home and my parents found out about it.
My grandaddy always told me that "if a man's word isn't any good, then neither is he"
I feel like I am in a vast minority when I still follow these kinds of rules, but see so many people who are rude, loud, show little courtesy for others, little or no compassion, many seem to want what they want, and want it NOW, not seeming to care how that affects the rights of others.
My little dog has better manners and patience than many people I see.
You can call me an old fart if you want, but at least I am an old fart with manners.