I imagine it's a similar story to why the industrial revolution did not occur in ancient times, despite elaborate steam powered machinery being known technology: insufficient demand to promote scaling the technology into affordability / practicality. It probably took a master craftsman a year to make the Antikythera mechanism, and all it did was automate a fairly niche task that could be done relatively easily by hand anyway. It is fascinating to consider that there must have been many similar devices that we've never found, and tantalizing to wonder if there are other classes of ancient mechanical computer we're not aware of. But fundamentally, they're very very expensive toys, not ubiquitous household items like coins. Even if a thousand were made, which would take generations to do by hand, we would still be lucky to find just one.