Before CCW licenses were available, "some people" carried that way due to the requirement for "deep paranoid conceal" since if a person got made, arrest was the only option.
However, I've been told by those people that they never liked it. It would have been clumsy to draw and not so quick, either. Plus, you couldn't sit anywhere without feeling a hunk of steel jammed into your spine.
Now with legal CCW, the rare chance an officer might "think" you're carrying enough to ask for your legal license and then send you on your way makes small-of-back carry something "those people" will never do again.
Ironically with a legal license now, I've found that I can carry invisibly using a IWB holster with my Rohrbaugh in my front jeans pocket with the clip over the edge of the pocket.
With any shirt that hangs over it, there is no indication whatsoever I'm carrying, and if the clip shows by the shirt riding up just a little, it just looks like a cell phone in my pocket.
If only "those people" had known about the availability of such small pistols and great options for holtsters back when CCW licenses didn't exist.