The pool of people who are capable of collecting garbage is non-scarce, so the price for labor is relatively small compared to the social value it produces.
Advertising is so well rewarded because the attention of consumers is a very scarce resource, so companies put massive amounts of money into capturing some of that.
And public institutions may serve a useful function, but again seem to be mostly about civil service powerbroking and providing extremely safe employment.
There are certainly (often larger) nonprofits with a tendency of overpaying their leadership and/or pushing policies favored by their corporate funders. I would in this context however not conflate "most visible" (ie largest advertising budgets) with "most". Most nonprofits I have worked with are ran and operated by hardworking people on minimal budgets.