The answer is that they're from ~2013: before React etc. taught us how to make SPAs. It was an early attempt, so it sucks. JS is best when it "paves the cowpath" and takes something we could already do slowly in browser and gives us a better native API for same thing, like querySelector or IntersectionObserver or how there was no built in way to parse a query string before URLSearchParams. Anytime JS goes first, the API is crap, like the DOM Node APIs themselves.