It is reasonable to demand time to upgrade, so that there are no
interoperability problems. It is not reasonable to demand that this
7-bit garbage be allowed to remain on the network forever, at the
expense of all future implementors and users.
forever is a long time. and yet, even if all use of quoted-printable
were to cease today, there would still be a need for new MUAs to be
able to read old messages stored on servers for many more years, perhaps
using raw utf-8 in message headers wouldn't replace 2047. instead,
it would add yet another format that MUAs are expected to parse
and display. it would not reduce complexity, it would add to it.