I don't have a personal cell phone, just a phone provided by work. So, I usually don't take it with me. If I'm on my own time, it's not on anyway, that way I can avoid work related calls when I'm not at work.
If someone has one and they want to make a call I don't really care. It doesn't effect my enjoyment of the outdoors. If they want to sit with their nose to a screen all day, it's their loss.
In general though, I don't think there are many serious outdoors people that have a trouble with staying on the phone the whole time their out. Probably too, if I invite them and that's all they do, that's going to be the only time I invite them. Obviously enjoying the outdoors isn't their thing.