It would be the ease of duplicating someone elses shader node arrangement from an image post.  Or someone's description where setting are listed.  It's more like standardizing your preference setup.  At least in the United States, we have a visual concept how an inch appears.  And, I'm pretty sure our European cousins have a visual concept how a centimeter appears.  Since, Bagginsbill contributes regularly through image and text to the forum, he uses inches as his standard of measure, and Robyn and I have conformed as well.