As others have stated, banks do sell directly to buyers. In order for the bank to sell direct to buyers, the bank representative that handled the transaction would need to hold a real estate license.
In comparison, a developer/builder that owns a new home development, with model homes, either has direct employees who hold real estate licenses, or contracts with a real estate brokerage. Either way, the point of contact with the buyer and public is with a licensed real estate agent. The same would hold true for a bank. If the bank wanted to handle sales of properties in-house, the bank would need to employ licensed real estate agents. Whether the real estate licensee is contracted or an in-house employee, the bank has a cost on their end to handle the sale. I am not familiar with any banks who retain in-house licensees to process their retail sales to end buyers. There are legal restrictions that are prohibitive for that, as well.
The best advice is to find a buyer broker who will guide you a buyer. Working with someone who puts your interest first will yield you the best results. If/when you call the list agent of a bank owned property, that list agent has a legal obligation to work on behalf of the bank to sell the house for the most money the bank can get. Their goal is to sell one of the properties owned by the bank to whoever they can find to buy these properties. Many real estate agents who work representing banks do not like to work with buyers; some will. The agent who contracts with the bank to sell the bank's properties does not have a goal of getting you the best the deal.
If you hire a buyer agent to work for you, their goal will not be to sell a specific house to you; their goal will be to find you the best property that meets your needs and budget.