GMAT Critical Reasoning (CR) | Studies in restaurants show that the tips left by customers

I'm still not a huge fan of the explanation, though I somewhat understand it. I eliminated B because I feel that even someone under "financial pressure" (an ambiguous term, by the way), could be motivated to tip more.

The prompt question says that credit card holders who see a logo are willing to spend more, but it doesn't limit this finding to credit card holders who are not in debt. Many credit card holders carry some level of debt quite regularly and the prompt makes it sound like