Well, sort of. The problem is, if every web app assumes they can squueze whatever resources it can, it basically reduces your overall performance (and - if you are mobile - your battery life). It wouldn't be a problem if it was about apps actually requiring these resources (number crunching and other computationally intensive tasks). But we are talking about mundane tasks such as displaying a GUI here! It's just laziness on the part of everyone involved, and the end user suffers most.