Personally I find having the PPC as a co-processor under AmigaOS 3.x a very nice addition completely in line with the philosophy of the Amiga itself. Move CPU intensive tasks to co-processors... and when running 3.x, the PPC is nothing more than a co-processor.
You can use archivers, play MP3's, etc. where the big chunk of calculation work is handled by the PPC... provides a nice speedup while still running in the "true" classic OS - 3.x.
These cards fetch good value because they provide extra fun to the classic Amiga. Even though practical use of running something as AmigaOS4.1 on a classic box is limited, it's still fun. Which is exactly why we all keep these boxes running in the first place.
IMHO having additional hardware for these classical systems (Indivision, Deneb USB, PPC, ...) makes for continuing fun every day!
