It could be the fact that people who are younger grew up talking more online, and having less phone call experience? Just a thought! I'm 25 but I grew up mostly talking to my friends online, rather than the phone. Making phone calls for me is more anxiety inducing because they're solely judging me on my voice. At least in person, I can try to convince them I'm a normal human being, but that's harder to do over the phone, because there is no context for the most part.