Phrase of the Day: Horn

So, here's how it started...
Erne: You better get on the horn...
Me: Why would you get on the horn?  I mean, it's spiky and has got to be really uncomfortable to sit on...


Then the thought process...
Hmm... we say "get on the horn" to mean to call someone on the telephone... because back in the day they really did use animal horns to "call" for help, or to gather, etc...  
Joel 2:15 Blow the ram's horn in Jerusalem!  Announce a time of fasting; call the people together for a solemn meeting.  
I wonder why it is that most of the people who use the phrase have never actually blown an animal horn... Why do we hold onto these archaic phrases?  Why do they survive instead of being eclipsed by modern phrases?  "Ring them up"... "Get on the phone"...  "Get your cell out"... So many options, yet "get on the horn" still survives...  Will this phrase be around 2000 years from now?  
Do cultures that blow conch shells say "get on the conch?"  Do they "blow their own conch?"  
Would a deaf person be "tooting his own horn?" Why not, "he's signing his own glory?"  
The Pony Express riders... "they're carrying their own mail?"
Some cultures used to drink out of horns... when they'd get drunk, were they "on the horn?"
Hmm... one could go on and on I'm sure...