I think, that's a common misconception about randomness: It doesn't mean the number has to change with every roll of dice. On the contrary the longer the sequence large clusters of the same number will occur.

It's maybe not so counter-intuitive as the Birthday paradox, but maybe already showing how bad our intuition is at grasping randomness. Initially I had hoped about research on that, which is probably very hard. - Or not? Couldn't you look at the n-gram distributions of the data and look how much that is "random", i.e. are people avoiding clusters harder than they should?