Why are there no octagonal, radix 8, based scripts?
Eight is not an even power of two (23). Octagonal is not as orderly as binary, quaternary, and hexadecimal. Conversion between these three systems and octagonal is not as simple as decompiling/compiling one symbol into two or four other symbols. Octagonal does have a convenient number of symbols, but this also causes it to not specialize in compactness or simplicity. 12480 can be used to write octagonal, it is just not supported by the standard.