Eric Muller quoted from a Seybold Report, but... I think it's out of date.
Actually, I'm not talking about the "Gaiji Problem". It's a well-known
special case of needing things that aren't in the standard one is using;
but it's a private need.
As long as the system you're using lets you make a character & font for
your own purposes, you can use it. Most of those proprietary systems do
so. But most such existing systems start with something that is far less
complete than Unihan, and hence have greater need for utilizing home-grown
gaiji.
I would assert that given the 20,000 Unihan characters originally encoded,
topped off with what has been recently encoded, there should now be almost
zero need in any of the Han-using countries for any such Gaiji as "many
'unofficial' Kanji characters, mistakes and misinterpretations, and
seldom-used Kanji passed down for generations". Most of those things are
already covered by Unicode, and in fact FILLING THAT GAP has been the
primary purpose of the most recent tens of thousands of additional Han
characters.
Company logos are a different matter, of course, but rarely if ever need
to be publicly transmitted as characters.
So, while Japanese customers might have at one time needed to use
something like the PUA, nowadays they shouldn't need to. In any case, the
Gaiji of any one installation are installation-specific. In the past, they
have never been transmissable, so that doesn't demonstrate any need for
widespread transmission of PUA characters.
Rick
