Why do real estate agents want listings?

Where I live, the customary real estate commission is 6%. Also customarily, this commission is split 50–50 between the seller’s agent/broker and the buyer’s agent/broker (though the seller pays the entire commission).

Now, to earn that 3%, the seller’s agent typically works with the owner to decide what work needs to be done to fix up the property, arranges with vendors to do the work, schedules and oversees the work, arranges access to the property, and handles invoicing. The agent also works to stage the property, if this is called for. Then the agent has to market the property, including photos, videos, open houses, broker tours, and other advertising.

On the other hand, all a buyer’s agent has to do is drive the client around to see houses.

Of course, once an offer is made, I can see that the seller’s agent and the buyer’s agent work is about equal. They both have to negotiate, deal with inspections and contingencies, and see the deal through to closing. But before then, it seems to me that the seller (listing) agent has to work a lot harder.

So, why not just be a buyer’s agent, and avoid taking listings altogether? But in my area, the homes for sale inventory is extremely low and agents are anxious to get listings. Why is that?