Basically the target of companies is avoiding to employ programmers for native applications. These people cost money. And optimization cost money. So they opt to waste our resources. The new ThinkPad/MacBook with soldered RAM does cost us a lot but not them.
And if you just use Googles Chrome - which made all this possible with V8 - you still have a problem. Every website believes it is okay to load JS from literally everywhere and show any kind of animated media. Plus no ad-blocker.
And us, opening hundreds of tabs with Epiphany, Firefox, Safari or Chrome ;)