In general, I believe that the math standard is a useful tool in helping to understand the intent of the tolerances defined by ASME Y14.5M-1994. This is especially helpful when it comes to having a clear understanding of these tolerances and how they equate to methods used in our modern electronic design and manufacturing environment; which is primarily why this standard was written in the first place.
Take, for example, electronically deriving a datum plane from a collection of actual point data extracted from a workpiece. There are probably a dozen ways that it can be done mathematically, each yielding a somewhat different result. The Y14.5.1 standard provides some guidance as to the intent of the tolerance specification so that a standardized methodology can be followed; or a measurement uncertainty can be determined.
I have a copy of the Y14.5.1 myself, and I can probably count on one hand the number of times I've had to refer to it in the past 5 years. But, the few times I have used it saved a lot of time and effort on my part and, for me, was ultimately worth the initial cost of the book.
So, it's one of those things that you don't really need until you need it.
My two cents.
GDTGUY