Speaking of optimization, keep in mind this shows up at the top of the results page. Any of the "more optimal" streaming solutions would likely require more JS

Speaking of optimization, keep in mind this shows up at the top of the results page. Any of the "more optimal" streaming solutions would likely require more JS on the page, and thus make the page as a whole heavier and load slower, which is actually worse for Google as a whole. Looking at just this feature in isolation misses the real-world problems immediately surrounding it.