Phone Calls are Rude
If you're 30 or over, you may remember how back in the 80s and 90s, calling during dinner hours was considered rude. The hours between 5-7 were for the family, and you'd never have your meal interrupted by a phone call. But, maybe that was just a Midwest thing.
Prior to the phone, the main way to contact someone was via a letter. The first asynchronous form of human communication. Along comes the phone, and it basically kills most personal mail by fixing the latency problem. In fact, I don't think I've written a personal letter in my entire life. However, calls were a step backwards in a sense: phone calls are synchronous, you need to answer them and interact, or not get the message at all (answering machines aside).
With the Internet being so pervasive; email, texting, and instant messenger is in the progress of killing the phone. The only phone calls I make now seem to be to customer service departments. I don't even call for takeout/delivery anymore, now that you can do that online. Obviously, the need for live communication will never disappear, but there are plenty of better, unintrusive ways, to contact people that let them respond on their own time and leisure.
When I get a phone call now, I interpret it as someone saying: Stop doing whatever you are doing now, because whatever I am calling about is more important than that. Chances are, it really wasn't. Phone calls are rude.
Obviously, family and close friends are exempt... usually.