Why Do Banks Sponsor visas

Banks sponsor for many different reasons, but IMO I think because of these important three things: 1) The people who they are sponsoring, are more likely to stay at the firm longer since they'll be "loyal" or "thankful" with them since the company is helping them a lot with the VISA situation; also because they would need to find another firm that would sponsor them. 2) Diversity; people coming from different parts of the world can bring expertise from wherever they are from, including knowledge about their region, a different language, or network. 3) Sponsoring for major firms shouldn't be big trouble for them. I mean paying for the VISA process represents cents for them, so if they like an international candidate more than a US citizen candidate, why shouldn't they hire them? Banks always want the best talent out there, so if you are an international students who is very talented, than as a bank makes sense to recruit them.