The Multiple Listing Service (MLS) runs on a computer and as such is totally literal. An agent must input the exact search criteria that matches a listing or nothing happens. The listing is lost like the proverbial needle in a hay stack.
Moreover, buyers often buy properties significantly different from their stated requirements. These too are lost unless the agent actively searches for them.
By presenting the listing directly to the members of the MLS by phone, fax, text, and email the property for sale becomes vivid and real in a way no computer can approach. This gives the agent the opportunity to present listings beyond what a buyers specifies. This can result in a greatly enlarged buying pool for any listing. The more buyers the listing is presented to the greater the opportunity for a sale at top dollar.
In addition, presenting a listing beyond the MLS assures the agent that the home is worth showing and that they will not be embarrassed in front of their buyers.