I have a bag of 36d6 dice I use for big damage. I find it simpler because it is consistent with rolling everything else (where else do you multiply?) and also because the first roll doesn't make or break the whole thing. If you have to roll 2d6 for a sneak attack or 12d6 for dragon breath you don't roll once and multiply it by the number you're supposed to roll. The benefit is if you roll a 1 on a d6 you have a chance to do more than 2 plus the modifier, the drawback is if you roll a 6 you have a chance to do less than 12 plus the modifier for damage. 5th edition rules (which DnD Beyond is concerned with) have you rolling double the dice. It's common because many DMs carried the practice over from earlier editions either knowingly or because they confused the rules between editions.
