I play in all keys, but I was classically trained, so I had no choice but to be flexible. I think playing in all keys is a matter of intelligent practice, not just random practice. The idea is that you want your fingers to be comfortable with the positioning that comes with every key because you're dealing with a difference in the distance between the notes and your fingers, which creates the chords for each key. If your hands aren't familiar/comfortable with moving around on the keyboard, then it seems really difficult to play in every key. When I started out playing for church, I would specifically do songs a half step lower or higher than the recording or force myself to do key-changes if the song allowed and the voices could handle it, just to challenge myself......just my thoughts.