I think I have the answer!

It is because the listing realtor doesn't return call from the buyer broker.

If the buyer broker has clients that would like to make an offer, then feel free Mr. Lister to answer your phone and answer his questions.

If you aren't returnung calls asap, then you are not doing your fiduciary duty. If my clients buy another house, because you never communicated to me, then you have done a poor job...

You mister Realtor, get this!