While I don't doubt that trying to "show off" or "job security" is a reason, I think another big one is because too many developers have no knowledge of the low-level basics to even consider that things could be simpler, having only been exposed to overengineered code and indoctrinated in the belief of abstractions as the ultimate panacea. To relate to the example of React and JS in the article, there are likely many web developers now who have never written a single plain HTML page and always started with the minimum React SPA, so they don't realise the former is even possible.