What he means is that, in olden days, videos would just keep buffering until the whole video was loaded. Now it's only at most the next ~1min, no more. You were able to see the grey bar thingie go all the way to the end.
Some people's internet and hard drives would be crippled by this. It's to promote multitasking mostly. There are ways to download videos that I won't get into, but it is possible if you desperately want to buffer the whole video. I do think it's stupid to lock offline video downlaods behind a subscription paywall, but I am small fry and will do what I can.
Not at all. If your hard drive would get crippled by a few GBs then I don't know what to tell you. When the playback is stopped, and the application closed, then the temporary files are discarded.
The argument about bandwidth usage is accurate though. I didn't make sense to buffer the whole video when it might not be watched anyways.
For longer videos, a lot of people will stop watching before the video ends. A lot of bandwidth is wasted by buffering the entire video when the user is only going to watch 50% of it. To save bandwidth, sites like YouTube only buffer a tiny bit at a time.
