I've spent along time studing traditional harmony from all the best regraded books such as Piston, Kosta, Gaulding, Aldwell and Schachtner etc. But all they do is teach you how to construct four part chorals. The reason usually given for this in the texts is that all of the music under consideration is essentially just "activeated" four part chorales. But my teacher has told me that this is just not true and the principles of four part harmony you spend years learning are just never used.
So my question is why bother learning it at all in the first place if all you do is just throw it all away?