Ringing people on speakerphone

Why do people feel the need to call comeone, put their phone on speakerphone, and then subject everyone in the office to the sound of the phone ringing? Is it less annoying to be waiting when you can annoy your colleagues? Are you under the impression that other people are going to be impressed with your phoning skills? Or do you genuinely not understand that it's really annoying to put your own desire not to have to handle the phone above others' desire not to have to listen to yet another annoying noise in the course of their day?