You are forgetting an important demographic of many households who do not yet have personal phones but are perfectly capable of communicating verbally: small children.

Amazon is betting on these children growing up with an Echo in the home which can be a nice way to catch up with your kids' activities while still at work or on your way home.

Child: "Alexa, record a message for mom."

Alexa: "Recording message."

Child: "Mummy, don't be late. But you promised to undo my hair when you return from work. My head hurts."

When I talk to my mother or father, we both put each other on speakerphone. On my end, my wife and I can both talk at the sime time... on their end, they can also have multiple people talking at the same time. This is a 2-endpoint call with 2+n users.

All Echos have better mics and better sound than my cellphone for this use.

I quite often call a house, or wish I could. We eat dinner with my mom most nights, and my grandma if she cares to come. "Whoever's there: dinner's ready!" is a message we have to send to their house, every day, and all we have to do it with is their two cell phones. I'm counting the days until we can call their Echo Dot instead.