Everytime I try to mix it up and say "hey, what's up?" or "what's good?" to random people they reply with "uhhhh, hi" or "what?" like they don't know what the fuck I'm talking about.
Thomas Watson started working with Alexander Graham Bell in 1874. Watson was only 22 years old when he heard Bell speak to him over the telephone. Bell wanted people to answer the phone "Hoy! Hoy!" as if calling a ship. Watson thought people should answer "Hello". Watson's idea took hold.