That's why first/business class tickets cost so damn much - to blind the traveler into believing that they're actually paying for something worthwhile. As it turns out, for many of them, it is worthwhile just to have shorter lines.
Theme parks do the same thing: pay more for shorter lines. Many attractions, such as the Sears Tower (still can't bring myself to use its official name) Observation Deck, do the same thing.
It's a money grab for sure, just not by the TSA. and why should the TSA give a shit about it if the first class passenger gets the same screening?
Wait, what? I am always frustrated at seeing the folks in those shorter lines (though I settle down at roughly the point of view others have expressed in this thread, that paying for shorter lines is a fact of all parts of life and doesn't seem to abrogate any fundamental right of mine), but it has never occurred to me to think that someone in one of them is lengthening my wait time. If anything, then he or she is shortening it by not being in my line.
Maybe your point is that the screeners for those short lines could be re-deployed to relieve some of the pressure on the longer ones, if the shorter lines didn't exist at all; but, given that they do exist, no-one's use of them seems to me to have any effect on my wait time.
On a side note, I've noticed that, given the speed that the first agent checks your ID and boarding pass, it's clear to me that they're only looking for three things: 1) you physically have your ID (not that it matches), 2) you have your boarding pass looks vaguely legit, and 3) if you have a precheck or priority marking on the pass that lets you go in a different line. That's really it; they're not really doing anything security-related. #1 and #2 are really more about making sure you don't get in the security line, wait who knows how long, get to the front, and have to get kicked back out for lacking your ID and BP.