In Japan, there are a lot of existing systems implemented based on the
interpretation so that we cannot change all of them now.
Nobody is suggesting that you should change all your existing systems
now.
I think the important facts are these:
i) much of the world does not understand ISO-2022, therefore if you send
unlabelled ISO-2022, there is a high probability that the recipient will
not know nor see what you intended;
ii) by using MIME to label your use of ISO-2022, you give the recipient
a way to know (at least, and maybe see) what you intended.
MIME is `on your side': a trivial change to user agents (or gateways)
enables you to send ISO-2022 messages unambiguously to anywhere in the
world.
It is entirely up to you whether or not you take advantage of MIME. If
you prefer to believe that all the world already understands ISO-2022,
and MIME charset labelling is unnecessary, you are free to do so (but
many people will not be able to read your messages).
Tim.