I think it's just a tradition in the electronics world to write and publish hobby and educational articles. It dates back to well before the the Internet. People enjoy this interaction, and the distributors give them space for it.

People like HVAC installers -- I've seen most of that on YouTube, where there's a chance of monetizing the content. I've repaired nearly every appliance in my house, thanks to blogs and videos posted by strangers.

Indeed. Vancouver Carpenter got me through a minor drywall repair job.