I stipulate that there are agents out there that are no good.

As for a "busload of agents", these are the absolute lowest quality showings your home will ever get. That's not to say that something good won't ever come out of them, but they're main function is to do exactly what they did in your case. You get the home all fixed up perfectly, turn on all the lights, get your hopes up and leave the house so that the agent can bring over the caravan tour, or office tour, or whatever. You leave excited about the prospect of today being the day the buyer finds you.

Instead, a caravan of 20 sedans pull up in front of your house, 50 agents walk in the front door and drop their card on your kitchen counter and walk back out the door. Most won't go upstairs or even open the slider to the back door. Back to the car and on to the next house. I'm not kidding when I say less than 60 seconds in the house. A good number of those cards are even lenders and escrow officers, they don't even represent buyers, they just want to BS with the agents and try go get their business while driving around.

You come home and say "WOW, this agent ROCKS. Look at all these showings! like 40 just today, that old agent sucked he could never do this".

If I want to have this caravan come to my listing and leave 40 cards to impress my seller, I MUST go on the caravan the week before and be one of the ones to drop my card in your listing.
Do I have a buyer in your price range? No
Do I have an interest in selling your house? No
Do I have a buyer that wants a big family 4 bedroom? No

But I left you my card so you can think your agent is amazing. He may do the same for me next week, but probably not. He won't be on tour next week because he already had the 40 cards dropped at his listing this week. I tell all my sellers this straight up, I tell them I'd be happy to do it, but they'll have to make the house look it's best for nothing more than a pile of cards. Every single seller has opted to skip it.

On the other hand, a broker open house works a little bit better. Those are the open houses you may see being held on a weekday. For those, I hold the home open from 11-2 or something and offer any agent that comes by a free catered lunch. The lunch gets them to the house, but in the case of a broker open house, I'm there to sell them on the home. They may not have a client in mind at the moment, but if I can sell the agent sometimes that will encourage them to talk to a previous client that may be looking to move up or down. These showings are much more effective because the agents linger, chat, look around and often time strategy can be developed in talking with other successful agents. They may go back to their offices and tell a coworker about this fantastic property they just saw on broker tour.

Plus, I leave a bunch of leftovers in your fridge for your family meal that night.