Nowadays, if your network is bad, you can just forget it. Every single media site seem to have migrated into this format at around the same time. It's obviously to stop downloaders, what it evidently didn't, but it will never change back.
There is probably a lot of code sharing among all platforms such that companies don't want to support two different buffering flows.
If you really want to play things multiple times, you can probably muck with your browser's cache settings, just tell it to cache a ton. I used to do that in Firefox when my mobile connection sucked, so I could buffer it all up and then just watch. Or easier yet, just use a download tool.
But this is a "me" solution, and I'd imagine those sites would like to be accessible for more people. (I'm personally a very bad "customer" for them.)
Anyway, it's a mild annoyance for me (I have that "me" solution), and not really my problem to solve.