There may not be a good reason. The only thing that comes to mind is if the code at the time had neutrals tied to ground at the entry panel to homes....
Thinking you could have searched for them at the FarmStore or Tractor Supply lead me on a wild goose chase that led me to realize you may have found...
Dad is a carpenter so grew up around tools and construction sites. Went to college for industrial mechanics and spent a few years as a field service tech in the corrugated container and pump field. Currently work inside sales and application engineering for industrial pumping equipment. I am an avid woodworker and outdoorsman, particularly working with hand tools and duck hunting.