Some users do want people to be able to connect to them directly though, hence Universal Plug and Play (UPnP), which can open ports on your router. You may disagree with the wisdom of automating the port forwarding process for people who don't understand networking concepts but there are people that do want other people to be able to connect to them directly, even if you don't.

Generalizing that one use case will suits everybody, fits about as well as one-size-fits-all clothing. Which never fits right.

Those that want or need a public IP can pay for it. I do. As you say, there is no one-size-fits-all.

This is why we are stuck with huge corporations to provide services to connect to each other. We are sacrificing privacy because we don't want direct connections. We could have hosted an Instagram clone at home as well if NAT wasn't there.

Ability to connect directly does not necessarily mean that you are somehow more vulnerable to attack. There are measures that you can take to prevent attacks from happening. It's trivial to configure.