[itsjustme2]

I agree. And I don't think you need to understand probability to see that a flattened cube will fall on the top and bottom more often than the edges. Another possibility in addition to what you mentioned is that the games the dice were used in took into account that some sides were more probable than others and people trial-and-errored until more-or-less appropriate payoffs/penalties emerged.

[SubiculumCode]

These were the points I was about to make.

Also, in modern dice when we want nonequal chance of outcomes we use two dice and sum. This wouldn't be needed if a die had unequal probabilities per face.