Top-of-wallet status is highly coveted because, once achieved, the incumbent – in this case the card issuer - has the advantage. Old habits die hard. Once a consumer develops a “go-to” card for certain types of purchases, they tend to repeat that pattern of behavior.
Those habits can be cultivated by offering benefits to the user via a rewards program. Sometimes the choice can be situational, with cardholders designating certain cards for specific types of purposes. This may extend to the type of card – e.g., debit or credit – and/or a workflow established by the merchant which makes it easier to use one card rather than another – e.g., Walgreens Express Pay.