A past clients asked me about the National Association of Realtors (NAR) loosing a lawsuit over conspiring to keep commission costs artificially high.  The case said that NAR rules and corporate practices lead to set pricing.  The crazy thing is that NAR internally in their conferences and meetings never talks about a set commission amount.  That would be a violation of anti-trust, so Realtors, as a policy, don’t talk about that in their conferences and classes.  
When you list a home for sale, the documentation gives a total commission to be paid, and then says that 1/2 of that commission will go to a buyer’s agent if a buyer comes along with their own agent.  If a seller were to decide to not pay a buyer’s agent’s commission, you would have less buyer’s agents promoting your property to their buyers.  Then you would have fewer people bidding on your property meaning a lower price for your home.  
Home buyers who do not have an agent will typically make offers that are not competitive with the current market, so they become a lost opportunity for your home.
NAR is appealing the ruling, so we’ll see what happens.