With Windows Microsoft was caught in the trap of misunderstanding that software development is not like any other industry. Pieces of software do not wear out if you use them a lot, so there is no demand driven by the need for replacement or repair
(1). Once a given problem is properly solved in software, there is very little room for further improvement (compared to other industries) and if any occurs it’s rarely perceived by the customer as worth paying for. You can’t sell a copy of an operating system and hope the user will come to you after 3 years to get a new version: it doesn’t have 2× larger image sensor, it’s not 2× faster, it doesn’t come packed with three times more features, it’s not half as cheap to run. As long as there are some things you didn’t solved in your product, you may expect demand, but later you end up with a product you must maintain indefinitely despite no one wants to pay for it anymore. With hope that perhaps technological progress will create new problems to solve, and forcing the customers to pay by preventing them from getting updates for older versions.
(2)Companies like Microsoft are built on the belief many early programmers had: that software development is not different than other industries, but they can develop a product once and then forever profit from it with little effort. Reality has shown that that effort is far from being small, but at the time no one knew this. But software development is different. Some of the differences were patched using state interventionism and creating the artificial market. Some other issues were addressed by practices like cutting users off from updates, intentionally introducing icompatibilities, damaging official documentation, producing problem to solve etc. But one can’t make money forever by going against reality.
Though I would be happy to see the world without Microsoft, I doubt there are any reasons to think they will fall anytime soon. The company may simply do what they were always doing: buy a product at bargain price from another company, polish it a bit, rebrand it as their own, sell at much higher price, and if competition comes — just FUD or EEE them.
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(1) Though Windows is somehow an exception and requires periodic reinstalls or at least heavy renovation.
(2) Not to be confused with the general EOL of LTS versions, which is only about platform stability.