IMO Internet in general is now 8-bit and I'm not sure that contemporary
should be so stick to the archaic ARPANET 7-bit world. Of course you can
rise the objection that RFCs states otherwise but (I understand that I'm
falling into heresy) RFCs themselves are subject to change.
Actually, the usual argument is that if you start sending blind 8-bit
without proper MIME encoding, you lose other vital information, including
what character set to use. Since there is no single all-encompassing 8-bit
character set, MIME encoding is essential in letting the email client know
how to display 8-bit messages. For example, if a person in Russia sends
8-bit characters without MIME encoding to somebody in Korea, the email
client in Korea will render the 8-bit characters using its local character
set instead of the Russian set, potentially making the message unreadable.