> I always saw the problem as: only one company or limited companies can manufacture them.

That is a really odd assumption. There are multiple companies making electrophoretic displays and multiple different technologies, of which only one is really commercially effective so far in a very limited niche space. Why don't you think physics is the limitation? I mean, don't you think above would be the equivalent of me saying that the reason we don't have daily flights to Mars is because SpaceX is the only manufacturer of Falcon Heavy.