I love the idea of bare-metal ports to the Pi. I saw snakeware posted here not too long ago. Are there other examples? ColorForth would be interesting as well
I especially like this Commodore 64 emulator (also based on circle): https://github.com/randyrossi/bmc64
It doesn't take a lot of Linux know-how to boot you favorite interpreter from /etc/rc.local or replacing /sbin/init (losing the libraries again, but at least keeping the kernel with the filesystem, network support and all the hardware drivers).
All of this is not that relevant for running Smalltalk-80 on the Pi, since Smalltalk was running happily on 16-bit machines with one or a few MBs of RAM.
So I guess the ultimate reason for doing this is "it can be done" - for the fun of hacking :-).