The title currently on HN has dropped the quotes that are in the article title: the article is not titled Why don't you use dependent types? (i.e. asking that question of the readers) but is titled "Why don't you use dependent types?" (i.e. the author quotes that question and answers it in the blog post).

For what it's worth, the article is the author arguing why they don't personally use blah-blah (Dependent Types) despite being a leading academic in the field (PLT) where blah-blah is frequently touted as the holy grail of that field, and justifies his experience using blah-blah-2 (Higher Order Logic), a tried and true "sophomoric" choice that seems dusty and crusty by comparison (literally, PLT undergrads learn how to formalize systems using blah-blah-2-reduced frequently in their sophomore years, as a way to learn SML). The rest of the article is really only interesting for the PLT/proof automation community since it is pretty niche. His conclusions is that you don't need the shiny new blah-blah to do things, often in more complicated ways, if older blah-blah-2s can do things mostly just as well and have the benefit of simplicity and ease of automation.