Problem with that is, once a seat is installed, it's installed and only needs maintenance every so often. With matresses, you need to stock matresses for every seat, load them for the flights, out and back, ideally some spares just in case of spillage etc.
Then after return, they need to be unloaded, shipped off to be cleaned or replaced, and a new set needs to be loaded. Having separate matresses per seat variant would be quite difficult to handle with Allegris.
Still... I do agree that the one shown is pityful.