Earlier quoted context omitted.
That's because this video is the sixth in the series. The first video goes into all those details. The setup is meaningful to people who want to know how it was filmed. If you don't care for it you can always skip it. Why ask for the video to have less content that other people might want to watch just because you don't?
I mean, that's kinda like saying "why skip ads, someone made that content" or "why not watch whatever is on the tv on whatever channel happens to be open with you turn it on". People like different things, and tastes change with mood, timing, etc.
Ads are content with an ulterior purpose of, well, advertising.
And the suggestion to skip is precisely the opposite of "just watch whatever's on TV", it's more of "if you don't like that channel, why don't you switch to another one?"
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Regardless, the argument is not whether or not one should watch the behind-the-scenes content, it's the existence of the content in the first place. If the behind-the-scenes is there, you can skip it if you want, but if it is not, then the one who wants to know how it was filmed will be left with no options.
Of course it doesn't mean it has to all be on the same video, but the nature of social video platforms ends up requiring that, otherwise the BTS is monetarily inefficient (if the channel in question is in it for the money).