In the good ol' days, when a person made a phone call and the phone was busy, he called back later. Today, there is "call waiting". "Call waiting" corrupts a person's character. Why? Because if Reuven is talking to Shimon there is no reason he should interrupt and talk to Levi. Why is Levi more important than Shimon? And if he were talking to Levi he would interrupt and talk to Shimon. So it is not a matter of who is more important, rather people just feel they have to interrupt the conversation that they are having and speak to whomever else is calling.
This is rude. Putting a person on hold is [almost always] rude. Even the click in the middle of the conversation is not necessary. It is just an annoyance.
I wish there was no such thing as 'call waiting'.