Robert,
I'll add a little. Many, if not all, original sporters had the 3-way safety, I think. I have a 1949 Husqvarna 8mm with a 3-way, military style safety. This rifle may be old, but it was designed for civilian hunting use. My guess is that scopes were uncommon back in the day, so no need to alter a perfectly functioning and easy safety.
Didn't the Springfield '03 have the same safety?
There doesn't seem to be any need for a company to invest in an alteration that at the time was unnecessary. The fact that every parts supplier has replacement safeties indicates to me that there must be a market out there and that there are many, many 3-way safeties around--and they can't all be from military surplus rifles