The Torah is a Chiyuv, not just good advice. The Mitzvos are Gezeiros Melech. Delving into the reasoning helps relate to the Mitzva and therefore to accomplish more with it. But we never know the full reason, which is why we need the 13 methods of deriving Torah. The Pasuk says, ??? ???? ????? ?? ???? ????? ???.
The greatest Chiddush I’ve seen yet is to call Leshem Hashem, Shelo Lishma, and Leshem yourself, Lishma.