Hole punching works for applications that are designed for it, and can invoke the coordinator. Sometimes, you just want plain old incoming connection (in my case, VPN).

BTH, I've never tested whether it works with CGNAT or not. It would be additional hop to jump if I would give up my IPv4 address, which obviously I'm not going to.

End user residential connections usually need a DynDNS as there's no guarantee you'll get the same IP for any foreseeable time period. So dynDNS could be bundled with hole punching. (It just allocates a port on the CGNAT, due to cost concerns I'm guessing these are rather dumb TCP/UDP devices, so almost anything will work through them.)

Of course it's a lot messier than getting a static private address allocated.

This will not help you if you have something like an IP camera that you want to access from outside your home, since the address will change frequently.

The only good thing about UPC/Liberty global's implementation of DS lite (now "Ziggo" where I live) is that they will switch it back to IPv4 with a single phone call to the help desk. I can live without IPv6, I cannot live without being able to reach my home server and IoT things.

For SoHo stuff people already need a DynDNS, and they could bundle that with NAT hole punching pretty easily.

Though of course it'd be nice to get a private static address.