It's probably in Google's interest to limit web bloat that degrades UX. AMP might be one strategy (with many negative aspects that many here will be familiar with), leveraging Chrome's browser share to impose limits might be another one.
Also reminds me on https://news.ycombinator.com/item?id=19038092 . I wonder if in the future we'll look at excessive JS bloat as we look at annoying pop-ups today.