In addition to different regulatory requirements (FAR vs JAR), there are differences in the application of common sense across the Atlantic divide*.
Historically Cat 2 – Cat 3 systems required frequent checking to meet the stringent reliability targets set by the certification standard.
Modern systems are much more reliable and used more frequently; some have self checking modules which alert the crew to unavailability at any time during flight.
I suspect that there are authorities who elect not to change rules until all systems can meet current standards, elsewhere rules are adapted and modified, dispensations granted, and systems evaluated on merit.
* excluding N of 49 N?