Design improvements are usually implemented incrementally, even granularly. Over time, however, the look and feel of advertising can evolve significantly when based on data that fuel content optimization: test, learn, apply.
The means of developing content and the facilities for distributing it have become democratized. New technology and the Internet allow creators of all sorts to bypass traditional gatekeepers and reach audiences of unprecedented size.
Why do we participate in so many of these platforms? I suggest it comes from a sense of not wanting to be left out. Not wanting to miss out on anything new. Who wants to be the one who says "Gee, no I didn't see that." It's the "if you're not current you're nowhere," state of mind.
We live in a day of TL;DR -- an abbreviation for "too long; didn't read." Weighing in at 1,090 words, this article qualifies for accusations of TL;DR. But if you made it this far, as only a meager 20% percent of visitors will do, you were obviously interested. Point proven.
Fights we see now are an attempt to maintain the networks' predominant position at the top of the pyramid. By using their most valuable content to leverage fees they want, the networks are being smart.