Backwards compatibility is mostly important when you have a large application base. However, there is hardly any application base left on the Amiga side - compared with Mac OS X, GNU/Linux and Windows.
It is still better than nothing. TCP/IP stacks, browsers, mailers,
paint programs,
development tools, text editors, archivers,
system monitors, pdf viewers, movie players, net radio streamers...
Besides that, machinecode for the PPC looks much better than x86 machinecode.
Uglier than m68k machine code... dealing with 32-bit constants is
pain.