The residential users don't need to have a globaly unique IP address.
That's like saying residential telephone users don't need to have a
phone number at which they can be reached. (after all, the purpose of
their residential phones is to call businesses for the purpose of
obtaining services, right?)
No, its not at all like saying that. Its like saying that residential
phone users don't need a globally unique circuit facilities assignment
(CFA) number. Indeed, most residential telephone users aren't aware of
that number, even though they have one. The globably unique telephone
number is more comparable to the email address, or the instant message
id.
only if you want to insist that every application that someone might
want to run at home should require an expensive external
infrastructure. (there are no polite words to describe people with
that attitude)