"Why did the market pick up NATs and run so hard with them despite their evident complications and technical compromises?"
The short answer is of course: because NAT was easier than either
(a) getting new addresses, or (b) renumbering.
Also, NAT adoption was a fairly gradual process. As far as I can remember, the first time I heard about it was as a Cisco feature but this was "straight" NAT where address range A was replaced with address range B without touching the port numbers. This was an enterprise feature for avoiding renumbering. Not much later "IP masquerading" showed up as a feature in the Linux firewalling mechanism and after that NAT started showing up in SOHO routers under names such as "single user account". Then at some point NAT became a more or less respectable technology rather than a dirty hack, just when applications that really don't mesh well with NAT, with the result that incompatibility with NAT became a problem for the application writers rather than for the user who was silly enough to try this flakey address translation thing.
3) IP address space conservation and ISP business models. ISPs feel that
they cannot give enough IP addresses to the users (e.g. home), unless they
want to spend considerable amount of energy fighting the respective RIR to
get the address space (e.g., our hostmaster boggled when I proposed he'd
apply for some /20 or /21 for a thousand or so DSL users).
Note that there is no good way for an ISP to give a customer just a few individual IP addresses. It's either a single address or a subnet, which means a minimum of 8 address of which 3 are wasted. And the RIRs require ISPs to register /29s or larger assignments individually in the database.
On the other
hand, some ISPs do even have a business model of not giving the home users
anything but one address, to get them to get premium service; I don't know
the details of such arrangements. The bottom line is that getting IP
addresses to those folks that need them (e.g. homes), _easily_, is just
too difficult, impossible or costs too much.
Yes, for many reasons, but the addresses being unavailable per se isn't one of them.
4) the evident complications and technical compromises are not really so
evident (as in, you don't typically notice or understand them outright,
and when you do, it's already too late), and your favourite vendor is more
than happy to code workarounds to these complications (e.g. ALG's) to gain
you as a customer.
Right.
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