Punishing glitch exploiters wouldn't help them sell cash cards.
People who get punished for glitch exploiting aren't very likely to thank the company for punishing them by buying cash cards, paying more money to get back what they already had, but what was snatched away from them.
However, many people who glitched money were foolish, and didn't glitch very much money. These people might eventually run out of money in the future, after new DLC and new things to buy are released. They might both be glitche exploiters and also cash card customers.
I know for my own part, if Rockstar punishes me for glitch exploiting, I won't buy cash cards or DLC from them in the future. If they don't punish me, I still won't buy cash cards, but I will buy DLC.
It is hard to believe that I am the only person with this disposition.
Since many people probably have this disposition, Rockstar stands to make more money by not punishing glitch exploiters than they do by punishing them.
The best business decision for rockstar to make is to remain consistent with their past behavior, and refrain from punishing glitch exploiters.
This analysis doesn't consider whether it is right or wrong to exploit glitches, or whether rockstar would be right or wrong in punishing them. It only shows that it would be in Rockstar's interest as a business not to punish them.
Companies, especially publicly held companies like Rockstar, have a tendency and even perhaps an obligation to act in their self-interest as a profit-making business.
If rockstar has this disposition, then it is not at all likely that they will punish glitch exploiters. And it is likely that they have this disposition, since they are a company, and further, a publicly held company.
This was one of the analyses I used when I chose to exploit glitches to make more money than I suppose I'll be able to spend. This was part of the cost-benefit analysis that I used.