We live in an age of instant communications.
You can send anybody, anywhere in the world a message instantly and for free on FaceArse, e-mail, Viber, Whatsap...
You can even talk to them for free and video call for free on Skype and others.
And yet people still send messages into radio stations requesting a song to be played for somebody and wishing them 'happy birthday' or whatever in the slim hope that they happen to be listening to that particular radio show at that time. A song incidentally that they could play for free at any time of the day or night on a multitude of music services...
It doesn't make sense.

It
did make sense when I was a kid and sending messages abroad (on those blue air-mail' letter things) was quite expensive and telephoning was extremely expensive. Also, there were few radio stations so there was an excellent chance that would be listening to the show.
But now...?