I have read in some detail (somewhere) a contemporary account of how the QWERTY layout was constructed. It was not as an obstruction to fast typing. The frequency of each pairing of characters in passages of standard business English were carefully analysed, and the most frequent pairs of consecutive letters were assigned to different hands and to widely separated columns of keys, to maximise the speed that could be achieved without clashing the mechanisms for keys raised in quick succession.

Once you have about 100 million trained typists on hand, it becomes difficult to introduce a new layout, even though a new electric mechanism does not have the same restrictions.

However, it seems rather likely that the qwerty layout would also tend to spread the workload fairly evenly over the digits, which may be preventing a lot of Repetitive Strain Injury that might arise if the layout was "optimised".

Benford's Law is sometimes evident in the speed of erosion of the lettering on numeric pads. However, items like phone numbers and prices do not have distributions that obey the Law - 0, 7, and 9 seem to dominate them.