Cluelessness. I think the ergonomic engineers live and work in a cable-farm vacuum, a virtual black-hole and figure that a 1/4x20 hole in the bottom of the camera will be all you need and maybe not at all since many of the newer cameras & lenses now have built-in IS so you don't really need a set of sticks.
However, the new grip for the Olympus Pen-F does have this feature, though you still have to buy it separately and still use the 1/4x20 hole.
I would be happy if the manufacturers would simply keep the bases consistent from model-to-model, especially for their constant iterations so that the custom plates I buy for one model will work on its replacement, instead of every model it's own.
For my m43 cameras, I've decided to have one custom L bracket for one body (expensive) and leave the rest generic (adequate and cheap) for simplicity and economy, though things seem to work fine simply changing the format from 4:3 to 1:1 for vertices, just like the good old days of shooting film with my 'blad and Rollieflex TLR.
Even on one of my high-res cameras, I said screw-it and simply used the older L-bracket though it doesn't fit perfectly, it does work. Simply getting tired of the hidden "upgrade tax" each newer camera takes to make it fit into workflow.