Since ITU approved the use of WAIC systems, aircraft designs have evolved and benefited greatly from fuel consumption savings, reduced maintenance (by removing/replacing costly and heavy cable wiring with wireless systems) and improved environmental footprint. However, these wonderful lightweight WAIC systems are restricted to provide bounded inflight services and does not provide air-to-ground or air-to-air communications. What is the reason for this?
WAIC is designed to be extremely low power.
Its low power is not be enough to reliably reach a receiver on the ground, satellite, or other aircraft. Increasing the power would create all sorts of other problems, including problems with spectrum allocation, and data collisions.
There is simply no demand for a more complex system to do these other tasks.
The basic engineering principle is KISS