It's just designers learning and overcorrecting sometimes.
Skeumorphism [1] tried to fix the confusing abstract and grey interfaces, but suffered from clutter and no-information-pixels. Minimal/Flat design attempted to remove unnecessary information but lacked affordances. Since then, these affordances have been slowly added back in. Currently, we're reconsidering skeumorphic elements without sacrificing what we've gained from the minimialst approach.
From each approach, lessons were learned and carried over.
(This is obviously simplified, but it's a better explanation than: "It's Apples fault")
[1]: https://images.squarespace-cdn.com/content/50144a1784ae6db4b...