Originally Posted by veganbikes

Japanese Industrial Standard. It is a crosspoint screwdriver that is a bit more precise than Phillips so you are less likely to cam out a screw. Shimano derailleurs use JIS screws and having a proper and precise tool to work on them I think is quite important.

I do understand you can work on limit screw and not cam it out with a Phillips if you are careful but as someone who strives to be a professional in the industry I want to use the proper tool. If you can have a tool that is designed for one screw and works better on another why the need for a Phillips screwdriver? I will admit yes the Phillips is easier to find but if you buy a quality tool you won't need to replace it often so heavy availability isn't as needed. However now with Park Tool's DSD-2 you can get one quite easily in the U.S. if you cannot find Vessel.