It's also, in some cases, about customer/public perception. A lot of buyers and their passengers have trouble breaking away from the Bleriot style even if the innovative designs are better - or older. Over the years a lot of "new" concepts have received the dreaded:
...
So, like the auto industry we keep seeing more of what granddad taught us was "right"
Rob
There is also the "tiny" issue of getting it certified by the FAA. Much, much easier to do the calculations and validations with a plain old wing-and-tube design.
All the above will probably keep Colani's designs from ever seeing the light of day.



This one came the closest; it was supposed to break the speed record for propeller driven aircraft:



It's on my list of FS aircraft to make "one of these days"; will have to get a few more under my belt before I could tackle it. It too, has anhedral.
-James