I think the execs at Microsoft have to make it look like they're busy, so they change around the interface every 10 years to justify their paycheques, even though the changes are completely unneccessary
Technology constantly moves forward so they have to add and drop features all the time. If you think Microsoft is bad you should try to use Adobe products. Each app like Photoshop, Illustrator, etc has a different interface. Worse, the steps do something like crop an image in Photoshop is totally different in the other apps.
Every new release has new features that sometimes break old features. Or there are bugs in Adobe products that have been in them forever. Adobe charges you every month for that priveledge.
There are better alternatives to Adobe products, but they're nearly useless because my industry has standardized on Adobe. We're locekd into Adobe because we need to share files with other businesses.