So it would be a better idea for the designers to think that they do _not_ know the use cases? .
Attempting to create a device that tries to please every use case known now and later will really please nobody. "Oh put a d-pad there... No, put two d-pads there! Put 5 keys on the top! Just in case... Somebody might come up with some use for them.".
I'd also say that real buttons are a poor substitute for the future technologies (not yet available) with proper haptics and visuals.