> I don't have a shortage of IPv4. Maybe my ISP or my VPN host do, I don't know.

Your ISP has paid 40€ for your IPv4 address. That's a cost they're most probably passing on to you.

> Every host routable from anywhere on the Internet? No thanks.

Every time you start a videoconference, there is a couple of seconds' pause while the peers perform NAT traversal.