Indoor free throws — a paradox of exercise

Outdoors I am a mediocre free throw shooter.  I hit 50 percent.  Indoors I hit about 70 percent.  This is close to the NBA average, and divided by my hourly wage it would put me at number one in the league.  How can this difference be?  Virginia is not that windy.  My outdoor free throw shooting is best when dusk is approaching, and the air is hot, thick, and still.  (I also feel I play tennis much better indoors, although that is harder to measure.)  The Great Outdoors are wonderful, but it is disturbing when the basketball clunks on the rim.  Each time I wonder what other life tasks I might perform much better, if only for some simple change in framing.   

Addendum: Forget free throws, here are videos of NBA dunks from the recent slam-dunk contest, courtesy of http://kottke.org.  My percentage there is the same, indoors or outdoors.