The biggest reason is probably that "true" Walsh drivers are 100% omnidirectional. Omnidirectional speakers are an acquired taste and getting them set up right away from walls, etc (to avoid early reflections that compromise imaging) is not practical for most.
Also the original Walsh drivers were full range but also inherently prone to self destruction and reliability issues over time. Not practical for most.
Hence the OHM "Walsh" CLS driver which addresses those issues and makes the design practical for many and I believe is also patented.
German Physiks DDD "Walsh" driver also addresses the reliability issue by punting on the bass. Those are also very pricey and have the usual omni placement issues so not for everyone.
OHM CLS takes a different approach and punts on the highest frequencies with the Walsh-style driver. A wide dispersion separate tweeter is used. CLS driver also facilitates placement closer to walls by physically attenuating Walsh driver output in rear and side directions inside the "cans".

