Something like that.
The devs want to use the latest frameworks and libraries, because it makes their CV look good. Or the bosses want them to use a CMS like Drupal (it's possible to build a slim Drupal site, but in practice everything is conspiring against you).
Brochure websites are typically written once, thrown over the wall to the client, and never edited again for 5 years. The client knows no better, the web-shop has been paid, and any techie reporting problems with bugs or performance is ignored.
I particularly deplore the custom of loading Javascript libraries from some CDN. If you do that, you're jamming code into my browser that you didn't write. It can change from one day to the next, without the website operator knowing that's happened, let alone reviewing the changes (I've never known such a review to happen).
There's a handful of sites I care about enough to make a NoScript exception (banking, government). Apart from those, if a site demands that I run arbitrary code on MY computer, and fails to load if I refuse, then there's always other sites. Byeee!