You don't speed up checkout because people care about faster checkout, you speed up checkout because people care about lower prices and faster checkout reduces

You don't speed up checkout because people care about faster checkout, you speed up checkout because people care about lower prices and faster checkout reduces fixed costs, or increases revenues allowing you to lower prices. If checkout lines are supply constrained (eg. there are always lines) then increasing speed increases throughput which increases revenues. If checkout lines aren't supply constrained (eg. there are empty checkout lines) then you can reduce the number of open lines without increasing wait times, reducing your headcount and driving down your labor costs. If you lower your labor costs you reduce your semi-variable costs and you can keep the same contribution margin and lower prices.