Slightly off-topic but now even New Yorker is inserting autoplay videos about completely unrelated topics in the middle of long articles (in my case "Anthony Bourdain on Going from Obama to Trump"). Why would they do such a thing? Are they hoping everyone suddenly develops ADHD?
I now browse with 4 extensions to handle issues like this. The autoplaying is everywhere and absurd. (NYTimes even has autoplaying animations you can't turn off. I sent them an email asking to have the option to turn it off as a paying subscriber and they didn't even respond.)
It's a mix of reasons, but it's usually ultimately about turning you into a product. I think it's disgusting.
To make the internet bearable, I use the following extensions:
Ad Block Plus
HTTPS Everywhere
Privacy Badger
And, the newest in the bunch, Ghostery.
I do have to twiddle some things on and off now and then, but on the whole it works and my online experience is a lot less jarring.