I inherited a project where an important dimension was supposed to be 12'-9" and instead it was established as 12'-9 9/64". The fraction rounds to 1/8", which resolves in the dimensions (12'-9 1/8"), so I have to fix it or customize the dim text, which would violate various Prime Directives.
And it's my fault I didn't catch it before adding all the pretty bits, which now have to be dragged and stretched by 9/64". But the point is that a project shouldn't leave schematics which such imprecisions.
It's just as easy easier to build precisely: Start, shift or guideline, 'R', value, done.
It doesn't mean you can't be sketchy in AC. Just rationalize the measurements before/as you go to DD. Even if you're not doing the CDs, be considerate of your colleagues and tighten up the model before it gets crazy-complex.
It is much more comfortable to work in a model that is precisely done. The mind becomes accustomed to seeing the nice round fractions, so when there is an ugly number, it gets your attention.
Eighths in dimensions at 1/4" scale make us look silly to the builder, except in rare circumstances. Unless you're talking about a funny angle, 1/8" has no effect on the design, and it will be ignored, unless chuckled at.
And no, you can't change the dimension standard to 1/4", because if your model is sloppy, the sloppiness will manifest as rounding errors rather than random eighths.
If the model is precise, the dims will take care of themselves, and you will have more time for other things.
So please model precisely, from the beginning. Banish all but the specialest eighths, and most of the quarters. Halves are OK... big and almost round.
One more thing. When you have 9/64" in a measurement, it's your fault. AC does not make these mistakes by itself, at least not as near the origin as we work. No mystery, just fix it and move on to something more interesting.