The point is to avoid breaking things. New versions remove or change APIs which breaks things. Even when interface is preserved, implementation changes can bre

The point is to avoid breaking things. New versions remove or change APIs which breaks things. Even when interface is preserved, implementation changes can break things. The new software may have a side effect that changes state somewhere and break things. Even something you think is an an independent island can break things. Because you might be using that island and it is therefore no longer an island but a dependency. Software can invoke a browser and expect it to be able to receive certain messages. Maybe it really is an island. A video game that mutates nothing, is used by no other software and is purely for human use. Maybe you are enjoying an RPG, but the devs decide to "balance" the power of some characters and it ruins the play style you were enjoying. There's trade offs to all things of course. But you can't have your cake and eat it to.