Square butts outnumber round butts. The majority of the Military & Police revolvers came with the square butt. It wasn't until the mid 1990s that S&W decided to produce most revolvers with round butts.
To me, anyways, it made sense to do this. It is easier to make a set of grips that transform a RB to SB than to do the opposite.
Besides, I like RB revolvers. They fit my smallish hand better.
