The catch is ethical. I personally don't feel good profiting from financial distress. Cash-back benefits are primarily funded through interest on carried balances (not interchange fees). In other words, credit card cash back is funded via high interest on other people's debt. The strongest predictors of revolving debt are income volatility, lack of regular savings, irregular work hours, and unexpected expenses. Basically credit cards act as an extractive safety net for people with no other options. It's a business model that depends on financial distress.