As has been pointed out; the breakfast isn't really free. Some motels will say that the breakfast is included in the cost of the room, which is a bit more truthful.
One motel that we frequently stay at in Billings gives patrons a voucher, good for a breakfast at their adjacent property. Weekend patrons are able to use the voucher for the breakfast buffet, which is very, very good. The rest of the week, patrons can order anything off the breakfast menu and use the voucher for the meal. I've stayed at motels that have a special breakfast menu that's "free" for motel patrons but the menu is quite limited on choices. One of the motels we've stayed at has a built on restaurant that is very convenient for guests but it isn't free. I actually prefer that option as it's convenient and if you do choose to eat elsewhere, you aren't being billed for other's meals with an imbedded and hidden charge for the room.