NYCJIM, you need to understand that in different situations, expectations of courteous behavior is different. I think you are bringing your classroom issues onto the hill.
I agree that any kid in your class on a phone is being rude. This is because in a classroom, you are the teacher. You should be the center of focus. You are trying to teach a class. The students should be focusing on you, not their phones.
At the dinner table with family or friends, the focus should be on the family and friends and the meal in front of you, that someone prepared for you. Again, in this case, being on the phone is rude.
Notice in both these situations, you are dealing with people that have a significant relationship with you. It's quite different on a ski hill with a stranger.
If I'm sitting on a chairlift with you and we do not know each other, how am I expected to behave? Are you saying that you are so important that all strangers must have a conversation with you? This might be the case if I'm with a friend on a chairlift. The friend is important enough that I should be engaged with him/her instead of my phone. But a stranger, I do not owe my attention if I do not care to (in this situation). You are quite high on your chair if you believe that you deserve a stranger's attention just because you are sitting next to him.
So suppose you turn down your egocentric views and I'm not expected to strike up a conversation with you. Then what? What else can I possibly be doing on a chairlift.
1. sit and look at stuff
2. text my friends on my iphone
You seem to think #1 is the only other possible alternative without being rude. So how exactly is #2 different from #1 from your perspective. Check all your senses - taste, touch, smell, sight, sound. Nothing is different in both scenarios except a slight change in what you see. Instead of my head up, my head might be down and my hands tucked to my body. Pretend there's no phone there....I just like to sit that way...does that change things? The only thing that's different is what's going on in your mind and how you choose to react to it.
I think you need to go re-read your book about being in the "now". I'm sure the book focuses on how you can enjoy your current moment to the fullest....not nitpick at others' actions and choices that have nothing to do with you. If you are letting others' actions get to you..regardless of the action, then you obviously have not achieved your zen that you speak of.