d6's make sense. It's the most common style of die in many games, and it's easier to lay hands on large quantities of them. Large numbers of d8s I think are an artifact of the scaling rules, but with most one-handed weapons and many classes having a d8 hit die, I think most gamers have a good number of them in their collection.
I'd be less certain that I could lay hands on 10d4 all at once, though. (And larger numbers of smaller dice are less random: the curve is heavily weighted toward the average. 10d4 could be simplified to '25' with a very high level of accuracy. Rolling 40 (or 10) on 10d4 would happen once in a million times.)
For things like this, I find it is important to remember that the game is centered on small groups of medium-sized humanoid combatants, and the further away from that you get, the more of an approximation things are. The scaling tables exist so that you can get a number for an arbitrary weapon in the hands of a Rune Giant or Iron Collossus, and maybe handle a template or enlarging magic, for the five rounds such a monster will be alive.
And I'd love it if those different tables would be made consistent, so that remembering the right answer instead of looking it up would be easier. But I don't think they have to be perfectly consistent with the differences at normal sizes. Because the cases that stress the table are short-lived (colossal monsters) or deliberate corner cases (Giant template repeatedly, stacking Improved Natural Attack with Strong Jaw....)