I am 52 and have NEVER needed to send a telegram. Long distance phone calls were reasonably affordable even before I was born.
I am amazed they were still doing it.
I think they were $20 or so to send. There was no real business purpose, but people were still sending them for the fun of it, like a unique birthday wish.
The only time I've needed to send telegrams were in the days of the Cold War. My grandparents lived in Czechoslovakia, and were not permitted to have a telephone. When the (intercepted and pre-read) snail mail was too slow for my purposes, I'd send a telegram. It wasn't private, but neither was the mail, and it reliably got there quickly. My only fear was that I'd scare my poor grandparents to death before they could read the telegram and see that it wasn't dire news.