Mind the gap: Why is there no general purpose ideographic system?

Morin has identified an intriguing puzzle about human communication systems, and one element of the solution: Inscriptional sign systems pose more coordination problems, making sender/receiver coadaptation more difficult. But I reject his view of written language, concluding that inscriptional sign systems can be generalist. The upshot is a cost-based proposal about why generalist ideographic systems are essentially unknown.