The most defensible framing that I came across (maybe from patio11?) in favor of credit card rewards is that they're a "bulk discount" on interchange fees. People who spend more on their cards also pay more fees (passed through the stuff they buy), so it kinda makes sense to give them a discount[1]. That's what credit cards do. Cards with the highest rewards are geared towards high spenders, with corresponding credit score and/or minimum income requirements. It's not unlike how the 2 quart (1.89L) bottle of mayo at costco is cheaper than the 8oz (0.24L) bottle from dollar general, but nobody would frame that as a "wealth transfer".

[1] of course, this doesn't need to rely on some principle that people are entitled to discounts if they buy more, because in reality discounts arise from complex market dynamics such as competition and price discrimination.