From the amicus brief:

This case concerns the authority of the Office of the Comptroller of the Currency (OCC) to extend the privileges of national banks to entities that do not accept deposits and are not banks in any traditional or legal sense. The foremost reason why non-banks will seek out a “special purpose national bank” is to take advantage of preemption of state consumer protection laws, particularly interest rate caps. High-cost predatory lenders are eager to evade state laws that limit them from charging usurious rates.