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CliffyB's Cock Holster
Playstation is a competing store front and a competing game console that plays physical copies if it was not obvious to you. Majority of Xbox revenue comes from actual game purchases rather than Game Pass if that was not obvious to you. They made their intentions of keeping the Minecraft IP completely transparent unlike Bethesda.
By your logic games from other studios like Obsidian and Ninja Theory should also be put on Playstation because "You cant ignore the install base of 100 million players"(Starfield and TES VI were not coming to last gen anyway).
Your view of this is so childish and simple-minded. They (MS) can do whatever they choose with product and IP that they own. Including putting titles like Ori on Nintendo platforms which are just as competitive as Sony's!
Do they do that day #1? No, of course not because they want to get the max impact in marketplaces where they don't have to share revenue with anyone and the long term benefit of association as the main place to play that product.
However, after sufficient time has passed and interest has faded, pushing it out onto a competitor is pretty good business. They get additional income, expand awareness of the IP (useful if its an ongoing franchise), and get to put their logo on the opposition's storefront.
If nothing else its a bargaining chip to get reciprocal concessions from a rival.
Just think it through. This is business not a playground game of one-upmanship.