My folks do the same thing- I think from being around when the telephone first came into the home and a call was a big deal. But it's not purely a generational thing as my 17 year-old daughter not only looks at the cell phone whenever it beckons, but even in-between (I guess to make sure it isn't broken).
Besides the risk of getting killed by someone on their phone while driving my other peeve (perhaps not nearly as important
) is being in a business face-to-face with someone and they stop working with me to answer the phone. Now the person on the phone has just moved in front of me as the customer service person tries to resolve their issue before returning to me. Happens ALL THE TIME- right? I whip out my phone and call the business just as they complete the call and proceed to pick up where we left off. It's fun to see their face when they realize the person they are talking to is 3 feet in front of them.