Does anybody know why so few states are available? Are there restrictions on mortgage companies as to what states they operate in, like there are for health in

Does anybody know why so few states are available? Are there restrictions on mortgage companies as to what states they operate in, like there are for health insurance companies? I've always been an advocate for states rights (a republic of states), but these sorts of things seem like they violate Article 1 Section 8 of the constitution in that they impede interstate commerce, and for little reason other than to favor one company over another, at the expense of the citizens.