[madmads]

YouTube videos have a much easier time reaching more people. Not only is video easier to consume than sitting down and reading for a lot of people, but YouTube also has a discovery system making your content easier to discover. I also believe it is probably easier to keep a lot of people watching a 10-20+ minute video rather than having them spend that amount of time reading too. The HN crowd might not fall into any of these categories though.

If the content is also just a stream of thoughts, it can be easier for some people to just talk to a camera, edit it down, and put it up as a video. For some people that is easier than having to think about wording, grammar, formatting, etc.

Hosting on YouTube is also free as opposed to hosting your own written website, but of course free hosting for written content exists too.