Practically everyone I play with is in standard tuning, and they can all play in most major keys. I always thought this was typical. Lots of purists want it to "sound just like _____________," and they show little creativity. We change keys to accomodate the lead singer, who might be different on every song. With banjos, we try to stay in G or A. Most of the fiddles and banjos can retune in less than a minute, so its no big deal.