Why do the COLORADO ROCKIES keep their BASEBALLS in a humidor?

SMOKIN FASTBALLS
   Tune into a Colorado Rockies game, and you're bound to hear one of the announcers mention the team's most well-known piece of lore: They store baseballs in a humidor. Wait, you may be asking yourself, aren't humidors used for cigars? Indeed, cigar aficionados keep their cigars in a humidity-controlled environment to prevent the tobacco leaves from drying out, which would affect their flavor. The Rockies aren't worried about the flavor of those baseballs, but rather about dried-out balls carrying farther and driving up scores. Why does this matter? Because Coors Field was well on it's way to developing a reputation as a park that was seriously unfriendly to pitchers---and very friendly to home runs.
   From the 1995 to 2001 seasons, National League pitchers at Coors Field recorded a horrendous earned run average (ERA) of 6.50, more than two runs a game higher than the 4.37 ERA recorded at other stadiums. Fans and the media attributed the numbers to Denver's mile-high thin air. But in the winter of 2002, based on a hunch that the balls might be drying out and losing weight in Denver's arid climate, engineers at Coors Field installed a humidor for storing game balls. Since then, N.L. pitchers have posted a 5.46 ERA at Coors. But N.L. scientists can't say exactly why it's so effective.
   According to a 2004 study by physicist David Kagan of California State University at Chico, keeping the balls at 50 percent relative humidity lowers their coefficient of restitution, a.k.a. bounciness. This means that humidified balls don't bounce off the bat as powerfully as dried-out ones do, making for a less batter-friendly pitch. Edmund Meyer and John Bohn, physics professors at the University of Colorado, later found that the added moisture does not change a ball's size and shape---and thus, its aerodynamics---which seems to verify Kagan's explanation for the humidor's success.