Ain't that the truth. You're right, they hold the upper hand, so you have to play the game.
Most of the time, HR isn't looking to fill any positions, they're just trying to keep the pipeline full for when a position comes open.
And don't get me started on Robert Half. Their reps don't get paid for filling positions, they must get paid for adding candidates to their "inventory."
Unless you're desperate, don't waste your time. You'll spend a couple of hours filling out paperwork and talking to the rep. After that, it's crickets.
They must be getting desperate, though. I received a call last week from them, wanting to "reconnect"...I've been gainfully employed for about 4 1/2 years (thankfully). I'll give him a courtesy call tomorrow, but that's about it. No one I know has had a good experience with them.
What I saw online about Robert Half wasn’t good. I had talked to someone there once when I came to learn that he wasn’t really interviewing me for an actual open position but for their files. And they try to worm information out of you like reference information at the managerial level (not to check up on you but to dig via cold call harassment for openings for other clients; I’m not about to sour my good contacts by having them spammed).