Odds are not favorable to a sign-value notation system as opposed to a positional value notation system thinking to use 2d10 to come up with '42'. I can't recall if they were sign or positional, but I would guess in roman numerals a large value with ten sided dice would be more likely to be created by thinking to paint two dice with a I, II, III, IV, V, X, L, C, D, and M each and adding them up, which wouldn't give you an even spread from smallest to highest value. To recognize how superfluous a d100 is you'd have to have a positional notation system, the base, 10 or otherwise, wouldn't matter. They could do it anyway but it would be a hell of a lot less obvious and sufficiently weird and counter-intuitive that it wouldn't likely show up in casual gaming. If base 6 is your system, you probably would have the 2d10 for 00-99 concept in the games rather than 2-12 bell curve on 7 we use, for instance. If your number system is sign or tally you'd like as not just roll more dice for bigger numbers and shrug off random distribution.

As to what the hell they used them for, it is probably fair to note that divination vs game can be fairly vague to the point of irrelevance, ditto teaching and games, since our ancestors knew and practiced the concept of Edu-tainment just as we do. If the things were reasonably cheap to make they probably would end up being used for tons of stuff.