Before the loading attribute on img, developers did have lots of custom solutions for lazy loading. A major point of lazy loading is to save resources on the server that would be wasted when serving an image that is never seen.
I like the loading attribute, but it hasn't been supported in Safari until very recently, so the solution has had to be a bespoke server + javascript solution to please Google. Still think a better solution is for the browser to optimize what is "below the fold" and make the decision based on user preference (I want to load the whole page). And most importantly, Google shouldn't weigh in on how to implement pages.
Before the loading attribute on img, developers did have lots of custom solutions for lazy loading. A major point of lazy loading is to save resources on the server that would be wasted when serving an image that is never seen.