Alright, guys. First off, it is not 'my logic', it is fact about pay phones and landlines. You make it sound like you're on call 24x7, in which case, I pity you. If you cannot afford some time off to just ride your bike without the distractions of everyday life, what a shame. I am not attacking you, I'm merely asking why life has to move so fast in general that you have to be that available? Are you the CEO of a Fortune 500 company?

Before you know it, we'll all accept that we have to be available 24x7 for whatever reason, then it's no longer life, it's work. I am on call every weekend. On my weekend rides, I turn the ringer up really high so there's no mistaking if someone calls. I stop, check the phone if I must, and do whatever is necessary. Nothing is so crucial that I have to have a headset in during my leisure time to immediately respond to a call. YMMV.

EDIT: Admittedly, life moves exponentially faster in this day and age. Availability and proliferation of information creates demands on our time that did not exist 35 years ago. I choose not to move as fast as the information curve.

My thoughts on the safety factor, while noting that I need to be available a large majority of time.

Risks:
1. Distracted
2. Can't hear as well,
3. Look like a crazy person talking to myself,
4. not as relaxed answering calls,

Benefits:
1. I'll actually ride my bike (I'd be too bored to do it otherwise),
2. Actually riding my bike will add more years to my life in terms of cardiovascular health than the minute increase in accident risk takes away,
3. I can keep my job,
4. I like to listen to music

So about equal, but number 1 and 2 of the benefits are the heavy hitters for me, and alone could outweigh the risks.