The thing about ULCCs shifting benefits to being dependent on being a cardholder is that I would bet a much higher percentage of ULCC customers would have difficulty getting or would be shut out of getting the card! They're competing with Greyhound, the curb bus companies and driving, after all. Would bet that a good number of ULCC tickets are purchased on debit cards rather than credit cards. When Barclay's Bank had the Spirit card during the great recession they were very picky about who they'd take, and paranoid about people instantly maxing with cash advances even though their interest rates were awful.

So if an airline like Frontier links too many benefits to a card that I'll bet 33-50% of their fliers can't get, then the have-nots get to feel like second-class citizens who (ironically) get to sit in the back of the plane (am sure they won't like that way of putting it).