I think we all know the answer to this. They want your money. If the features of the First Edition Lariat don't persuade you, maybe the color palette will. When you go to the Build & Price Tool and select Lariat and then select Rapid Red, a little popup comes up alerting you that doing so will raise the price by $5,870.
Not only is it more money for Ford, but it gives you obvious bragging rights. When you see a Rapid Red Maverick, you will know that that person dropped over 30k for a truck that starts at 20k.