It tends to be a weird two weeks too. If you know you're quitting you're usually already preparing for it prior— taking less responsibility, finding who to hand projects to, etc. In my experience at times it's just two uncomfortable weeks of showing up and doing nothing.
Also if you just leave it may be harder to get a decent reference from your colleagues for future jobs.
Personally, if it's a job I really dislike, I don't mind losing the extra $X,000. I've discovered through the years my mental health is worth a lot more. Once you leave a high-paying job for one that pays less, or even to just take a break and earn nothing, you start thinking about these sorts of little extras as inconsequential at best.
If the next job pays more than the last one, you could say it's a net loss for the employee too, since that's an extra two weeks one could've earned more.
But if neither of those apply, it's probably worth it to hang around and get some extra cash, or just get a couple more weeks of hanging at the job with "graduation goggles" and little work stress, yeah.