Not sure why this is but there is a thing that some people think they have the best boat there is and anything else is inferior in one way or another.
It's not confined to the canals. I know one couple who are particularly bad for this sort of thing.
To be honest I have no problem with and don't blame people if they do wish to live aboard and continuously cruise and not pay council tax. I don't think anyone really should be complaining about that as long as the continuous cruising is exactly what it should be. going back and forth on the same bit of canal isn't continuously cruising.
By the way not everyone pays council tax even if they do live in a house. eg older folk live with their adult children , anyone generally under the age of 18 and even folks like my next door neighbours sons who are in their 30's and still living with their parents.