"both Jews and proselytes, Cretans and Arabians — we hear them telling in our own tongues the mighty works of God." - Acts 2:11
I have a Subaru Outback. It can serve as a luggage carrier, shelter from rain and snow, mini concert hall and small conference center. But at the end of the day, this mighty motor driven vehicle has one foremost purpose in life: transportation. It gets me from point A to point B, and it does this admirably.
God bestowed spiritual gifts in a similar way. While the giftedness of believers may differ in many ways and be used to accomplish many goals, God has given them to expand His kingdom. They may be desired and nurtured for various reasons, but after all is said and done, these supernatural abilities have one foremost purpose: to glorify God by proclaiming his mighty works.