I think the main difference between choosing to hire contractors as opposed to permanent staff is if the work they are being hired to do is something that is a short duration project with a highly specific skill set. For example you might want to create an app for your business and hiring someone specialized in this would make sense. They could likely do it more efficiently and maintaining it later would not require such a high skill level and could be handled as part of the duties of one of your permanent staff.
The article is about startups mostly. There’re lots of non-technical founders who think they can outsource everything and build a company and it won’t work. I tried to provide some guidelines in the article.