i want to scream
The advantage to the Wanted: Players forum is that most people who are seeking a new game look there first. Browsing games works if you have some specifics of what you're looking for in mind...if you really like a specific system, or setting, or GM, things like that, so you can narrow your search. Otherwise, just browsing games is kind of like trying to take a sip from a fire hydrant...
But many players who are looking for something new, or something similar to what they've done before but not necessarily in the same system/setting/whatever, will go to W:P, because they know, immediately, that what's listed there is not only accepting new players, but is actively seeking them, and the listings can give you a brief overview of what the game is without even having to open the ad, if it's headlined properly.
I agree, listing in W:P isn't necessary. It is, however, more likely to get responses than just leaving your game floating in the Aether and hoping someone stumbles across it.