7.04 dropped PowerPC as a supported architecture after a decision by the technical board. It is now only a community supported port. See https://wiki.ubuntu.com/PowerPCReview
for more info.
There are still lots of PowerPC users and there is an active section on the forums. However the going is a bit tough. Gutsy required quite a few work arounds to boot the install CD, and there are plenty of long standing PowerPC specific bugs.
It would be great for powerpc to be supported again. Perhaps canonical could hire a PowerPC dev, or a ports dev.