Seems such a con. And your links imply it's built in to the system, there's always a 6% charge for that (otherwise why would they charge and give back half).
Short of multi-millionaires looking for an interesting fifth home without caring where it is, I don't see why you'd want to try to explain your requirements to someone else, have them sort of get it, show you things that aren't right for reasons you forgot to give or can't quite explain, and pay for the privilege.
In the UK we just find somewhere we like the look of, arrange viewing with the (sellers') estate agent, and potentially make an offer. What would a buyer's agent do for me except increase the price/decrease what I can afford?