Just a guess here, but millimeters are easier to understand in smaller numbers. For instance, 13mm=0.5118in; 12.5mm=0.4921in. Thus, while we all know that there is a huge difference between a 12.5mm shaft and a 13mm shaft, I doubt that many of us want to remember that we like a 0.492" shaft over a 0.512" shaft.
Dave
This came from the Ask the Cuemaker section, makes sense:
Quote:
Originally Posted by cueman
Many of the tips from way back came from France and were measured in millimeters. So it continued to be the standard. So that is how the public was educated on tip size. On the other hand USA Cuemakers started out using Dial Calipers to measure other dimensions just like all USA machinists use and that became the way they calculated all other measurements.