It is easy for a company building single page app to form an API, an analytics team, an infra team, QA, slapping incremental solution to solve their incremental problem. After having specialised team, it is far harder to merge things into good old Django with nginx where you can parse the log for analytics and just serve fully rendered html. At this point people will start saying their organization is different, we do it for "scale up" sake. They are probably right and the WhatsApp/instagram path is probably not for everyone.
Organization is the human version of software architecture. Do it too much, too early, too little understanding will all have long term, non-immediate, non-numerically justifiable effect. People love to talk about these.