When a seller sits down with their seller's agent (listing agent) they determine a buyer agent "offering" for a few reasons:
1) The seller wants as many agents as possible to show the home
2) The buyer is unknown, so the buyer agent fee is also an unknown on that day
3) The buyer will likely be financing the buyer agent fee in the sale price
Because the seller sets the asking price, the seller needs to "set aside" within that price, an amount sufficient for the buyer to hire representation, and pay for that representation, as part of the transaction. The seller does not tell the buyer and buyer's agent what that fee "should be". The seller simply sets in motion the means by which a buyer and his agent can fund their agreed upon commission.
Jack is correct that the seller offering "a bonus" for a buyer agent to "direct" a buyer to his home (in order to make more money), is an outdated and inappropriate offer. It is a "leftover" from the days when all agents represented the seller. Though the seller is free to use any means to entice a buyer, doing so by means of a bonus the buyer is not privy to, only made sense when ALL agents represented the seller back 20 or so years ago.
The mls offering is not what the agent for the buyer is "to be paid". It is an amount "set aside" to be discussed and decided between the buyer and the buyer's agent. Think of it as a "retainer".
An attorney may ask you to deposit $5,000 with him as a retainer. But if the final agreed upon price between the attorney and client is $200 an hour, and at the end the total monies needed to pay for the service is $4,000, then the attorney does not keep the remaining $1,000 from the retainer. Same with a buyer agent fee. If the seller offers 3%, but the commission understanding between the buyer and his agent is 2%, then the fact that 3% was "set aside" by the seller, does not change the agreement between the buyer and his agent.
While everyone is correct regarding "the rules we made for ourselves", at some point we have to understand that our clients, and in this case the client is the buyer and not the seller, are no longer going to sit still and watch us make our own rules and determine how much they will pay us, without their input.
The rules we made for ourselves when we ALL represented sellers of homes, and never buyers of homes...well, really. Does it make sense to anyone that we didn't sit down and change our rules back 15 to 20 years ago when buyer's attained representation? I don't think so, and neither do most buyers of homes.