Some people think the magic of the speakerphone is so you can hear someone when you’re driving without holding the phone to your ear (I said it before — don’t do that), and some people think that it’s great because multiple people in the same room can listen to one phone call (perhaps when the mom calls grandma and all the kids can listen in).
The TRUE magic of the speakerphone is multi-tasking. You can do quite a bit while your listening to hold music.
Many years ago I was in the tax business. If you’ve ever tried to call the IRS during tax season, you know that you can spend quite a bit of time on hold (and I’m willing to bet they haven’t changed the hold music since 2008). It’s really not very exciting to sit on hold. However, with the magic of the speakerphone, you can listen to the hold music and have two hands free to clean off a desk or reorganize a file drawer or sort receipts or anything that keeps one hand close to free to grab the phone when the other person picks up.