I suspect the real answer is because Microsoft wanted to monetize Minecraft in a way which was not possible with legacy sales. I bought minecraft back in alpha with the promise that I would get any and all updates and future editions for free with purchase. Microsoft legal saw that agreement and knew it was incompatible with their business goals. They knew that incorporating a microtransaction store would basically require unlimited currency for players like me who had purchased it long ago. So the “simple” answer was to re-implement the entire game without the legal encumbrance of the legacy purchases.

Yeah I’m just gonna have to take my old reddit strategy of rolling a new account once a month.