Well see this is where theory and concept work are a lot of fun.

Let's say that you make a transaction, and there was a minimal fee - now this is a just VERY Wild and outrageous example; but none the less makes it rather clear we think.

From your transaction we gain a fee. Now let's assume we use that fee, in part, to buy a packet of seeds. And let's say those seeds are planted, and they yield tomoatoes. In turn the tomatoes get sold. This yields a revenue. After the seed sale and farming and expense, etc., are paid, let's assume there is a profit.

The bank, having engaged in the producution fo the seed, through perhaps a 'branch of it's operations' like starting small businesses; would be paid a portion of those profits.

The bank then, rather than being solely concerned with gaining money, seeks to gain profits, and redistriute them across the accounts, in a more a humanistic harmonic manner.  Not with One Sole Goal of profits, but to make profits, and share them across the accounts as benefits or bonusus.

As I said wild. But clear.