Part of the failure to spread seems to be due to Bliss’s dogmatic resistance to allowing the system to adapt and be used for other purposes. His goal was to eliminate conflict by reducing misunderstandings, but he did this by insisting on rigid control of the language’s use. The protracted legal battle against the Ontario Crippled Children’s Centre was tragic and sadly ironic, as I do believe he had good intensions throughout. Maybe blissymbolics would have spread further as an open, organic system.
An excellent audio piece on Mr. Bliss is https://www.wnycstudios.org/story/257194-man-became-bliss