In some countries, NAT was implemented at the ISP level and you had no public IP at all. I remember it being a consistent practical barrier back in the 90s for

In some countries, NAT was implemented at the ISP level and you had no public IP at all. I remember it being a consistent practical barrier back in the 90s for stuff like file transfers. I had a public IP but the other person didn't and had no way of getting one or setting up port forwarding. Back when file transfers were often done with direct connection.