Why use a super accurate cartridge protractor

I believe that they are for those with younger eyes who wish to spend more time on alignment than most of us do. I have not used then myself as the arms I usually use, VPI and Graham, come with gauges that do a very good job. Would Mint etc do better, possibly but not with 70 year old eyes and nerves. The Graham is especially good as it comes with a gauge that fits over the detached arm wand so you can look DOWN through the gauge at the stylus instead of trying to look at it from the top. Also has device to set arm at correct piviot distance. I wish more arm makers would provide similar devices. I have been aligning cartridges since before most users had a sound system other than a baby rattle and appriciate its importance but it seems to border on an obsession with some.

The advantage of the Mint over a downloadable arc or two point protractor is its precision.

The drawn arc and null points of the Mint are very fine indeed and the flat mirrored surface allows you to adjust accurately to these lines (and of course the mirrored surface and guidelines at the null points assist in avoiding parallax errors).

But it will not save you from making those tiny adjustments - these are what the Mint is all about! You must make these micro adjustments to avail yourself of the Mint's precision. The precision possible with the Mint is much better than 0.5mm - Magnification is a must!
Like the designer, I recommend strong natural light if you can avail yourself of it.

Lots of confusing and conflicting info with regards to alignment-- Lofgren, Stephenson, Baerwald, Rega-- all different alignments, all compromises. I've been trying find a definitive answer, but I think the geometry is not sufficient to address tracking distortion errors, given the different vinyl properties, cutting methods, etc. I did find that on fine-line or shibata type styli, a careful alignment can improve the sound, but I do not think the change in sound was due to the alignment "exactly" matching any one particular recognized alignment scheme-- probably more just trial and error. I use a denneson soundtractor and have spent WAYYY to many hours trying to visually align the stylus-- not so sure its worth the effort though.