>> Why don't you want every device to have a public IP?

> Suddenly, your smart lightbulb is accessible by everyone. Not a great idea.

Why would it be "accessible by everyone"? My last ISP had IPv6 and my Asus (with the vendor firmware) didn't allow it. My printer automatically picked up an IPV6 address via SLACC and it was not "accessible by everyone" (I tried connecting to it externally).