cue`s once had a curley bit on the end and was held the other way round. the flat piece was were it it ran on the table. then someone turned the cue around used the thin end and his other hand as a bridge, latter the curley bit was cut off. hope you get idea
The flat bit was used on the table when a shot could not be reached, so the thin end would be held and the shot played with the thick end. This was and still is the way in the absence of a rest. The cue was allways used as now for reachable shots.
not all of them do.
Useful for knowing which way up your cue is though. Since the tip will never be completely symetrical or centrally placed on the end of the cue, it means you can use the cue the same way up all the time and your tip will behave the same.