Acquiring new credit card customers has become expensive for banks, with escalating signup bonuses. 50,000 or even 100,000 point offers are more expensive than the 15,000 points that were common 15 years ago. That only makes sense for banks if customers will spend a good amount of money on their card products over a long period of time, or rack up large fees (while paying off their balances).
Citibank just tweaked their rules about who they’ll give a bonus to. American Express will only give one bonus per card product in a customer’s lifetime.