I have written a lot about state licensing typically being more about protecting incumbents from competition than consumer protection. This is a story in a similar vein, where plumbers worked to stop the approval of waterless urinals because they required, well, fewer plumbers to install. In the end, there was a compromise -- the plumbers would support waterless urinals in the code, BUT the code would also say that water still had to be piped to the urinals that don't need water. I kid you not.
This reminds me of when railroads were switching from steam locomotives to diesel. The switch basically obsoleted the job of the fireman, who shoveled coal and kept the fire optimized in the boiler. Faced with extinction, the fireman's union followed a gutsy strategy -- they demanded that diesel locomotives have two firemen instead of one! You see where this is going. Eventually, they compromised at one, so for years, decades even, useless firemen were paid to ride around on locomotives.