Iirc, there were several people who had acute cardiac issues after using bk-2C-B, which was a bit of a buzzkill. Not a common side effect, but still. Add to that the fact that it would dimerize in water, that may (or may not) have contributed to the wide variability of dosages. The comeup was long, the duration was longer, and I imagine oral was the only practical way to take it because of dimerization. That meant that you had to take your dose and hope that you hit your mark. For some, that was 110mg. For others, that was 210mg. Pretty big commitment, especially with the heart issues appearing to largely be dose dependant I think.
Long story short, vendors had lots they couldn't offload for long periods of time, making them unwilling to invest in analogs.