We do about 2/3 of our sets in Standard, and 1/3 in Eb tuning.
I don't know why we have to do the Eb stuff. We have a female lead singer, and she can hit everything in Standard no problem. It doesn't really affect how the guitars and I play or sound all that much. I have raised this point to no avail.
I suppose, to the most sensitive ear, the EB tuning might make Hendrix, Stevie Ray Vaughn, and Kiss sound more faithful to the original. But what percentage of the audience is that? Some nights, I'm probably the only one who would notice.