The point being he's spending the $2000 anyway, so he'd rather get $40 back from his credit card company rather than $0 back if he used cash or debit.
Cash-back is "money", reward points (more or less) is "discount on given good".
The point being he's spending the $2000 anyway, so he'd rather get $40 back from his credit card company rather than $0 back if he used cash or debit.