Municipal water has all kinds of stuff in it (sorry to be so technical!) that orchids would never be exposed to in nature.
In the cloud forests there is no water hardness, chlorine, chloramine, Aldehydes,
Bromodichloromethane, Chloral Hydrate, Chlorodibromoacetic acid, Chloroform, Dichloroacetic Acid, Dichloroacetonitrile, Dichloro-2-propanone, Haloacetic Acids, Haloacetonitriles,Haloketones, Tribromoacetic acid, Trichloroacetic Acid, Trichloro-2-propanone-1,1,1
These are a few of the components that my municipal water is tested for!!
I guess if you want optimal performance from your plants, you would want optimal water quality.
I am switching to R/O!