I think the difference is that radios don't generally cause harm, damage or injury. All CASA has to do is have rules in place that if somebody is not legally operating the drone then it's no longer a CASA matter, it becomes a criminal matter and goes straight to law enforcement and the courts. If you cause damage to property or persons in the process and are operating illegally, good luck in court. That's what stops the majority of people building their own cars and/or driving unregistered, except for those who have nothing to lose anyway...
The problem UBER drivers have is the lack of legal protection, because they operate in a grey area they also are insured in a grey area. As damage and liability insurance costs mount for these drivers that will push their costs above taxi operators as they have agreements and policies in place to keep those sort of costs down, as well as some states having industry generated insurance, maintenance, policing all managed by their own taxi 'directorate'. CPVs are road rash magnets, as well as the liability insurance claims that will start to occur as people are injured, are late for work, etc etc... UBER themselves are smart, the driver wears it all, not to mention the lease rate on vehicles in climbing as well as the vehicles themselves costing more.
If you havn't noticed yet car insurance has been climbing faster than CPI or recent.