The only way for mafia to be wrong and not know how many times you've used the item is if you used it outside of mafia, and then why should mafia care, pressing the button would then gray it out and fail using the item. But you already used it that day, so what does it matter?
This is factually incorrect. We can get a response text from items that have preconditions applied to their usage that indicate a failure. Without mafia knowing what this text is, the presence of a response cannot necessarily indicate successful usage. I know it's a trivial example (but I really don't want to waste time hunting down a more relevant item simply to illustrate the same point), but the dusty animal skull has three different response texts when used. It is only when you have the 98 other bones needed that you get a successful use. Without explicitly hardcoding into mafia which of those three responses is the successful one, how would we know?
Currently, the only reason mafia's counters are off is if you adventure outside of that installation of mafia. Were we to introduce auto-incrementing, mafia would be off more often and not just on instances when the item had already been used.