Tunnels are used for all sorts of things, including some that aren't IP-shortage related (but many uses are related to IP shortage; connections between devices on private networks, for instance, and connecting IPv6 networks to IPv4 networks). But, I wasn't saying that all of those technologies only have application in solving IPv4 IP shortages, but they often have had a lot of effort expended on making the work for that purpose, because it's such a pervasive problem.
My point is that the IPv4 IP shortage is like the ocean and we're all fish swiming around in it. We don't see the water because it's all around us. But, it's shaped our thinking about networks in real ways that most people working in the field today have never had an "every device has a unique address" mindset. The inventors of the internet and some of the greatest innovators of networking existed in a world where "every device is addressable". I think that's a major difference in mindset and I think it has consequences.
My point is that the IPv4 IP shortage is like the ocean and we're all fish swiming around in it. We don't see the water because it's all around us. But, it's shaped our thinking about networks in real ways that most people working in the field today have never had an "every device has a unique address" mindset. The inventors of the internet and some of the greatest innovators of networking existed in a world where "every device is addressable". I think that's a major difference in mindset and I think it has consequences.