That's not really true. Most people, companies and consumers alike, have networks of more than one machine and they actually really want those networks to be pa

That's not really true. Most people, companies and consumers alike, have networks of more than one machine and they actually really want those networks to be part of the Internet rather than being separate and using a proxy. You can't do that without public address space. You can try to fake it with NAT, but that introduces a whole bunch of problems of its own which then need to be worked around. It doesn't make sense to use it unless you can't get public address space in the first place.