1. That didn't stop people blogging before :D
2. Money happened pretty much. First people started monetising their blogs, then they turned into books, which turned into multiple books and youtube channels and then it was no longer a blog and more of a company.
and additionally:
6. The younger generation is used to having their actual face plastered all over the internet and thus feel more natural making videos with their own face and voice.
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I, and I think a good part of the HN crowd, are in the generation where we had actual friends we only knew by their handle/nickname and never saw their face unless there was a meetup of some sort and we actually went there.
For me, using my own face, or even name, to present any sort of content just feels wrong in a visceral way.