Many reasons. First we have a national network of pre-approved vendors your agents have direct access to. They have been vetted and approved, but you can still customize which vendors you decide to display in your agent marketplace.
In addition you can build our your own broker marketplace.
First is you can create your own products like TC services, listing marketing services, or shared costs in other programs you buy for your agents.
You can create affiliate arrangements with vendors whom your agents need services from.
You can monetize your local client marketplace which is a client facing "craigs list" of local vendors.  This allows you to charge for access to your agents creating monthly residual income.