When they don't sell their stocks to pay their debts? They pay more interest in credit-cards than the long-term return they may get from stocks? Maybe they think they can default their credit-card payments while digging into their stock accounts?
Ha, I did this last year. Best decision I ever made. After some unemployment I had $15,000 in cc debt and an IRA that could have paid it off. Thank goodness I procrastinated.
About 10 years ago there was this guy I worked with that maxed his credit cards by getting cash advances. He got a little over $20k dollars, then opened up a margin account and put every single penny of it into Lucent (LU) Lucent was trading at about $41 or $42 per share. I remember he bought right before some news came out and and LU went to $45 the next few days. Then he said he wanted the price to go down so he could buy some more. Well, it went down....and down and down. I know he was still holding it when it was down to $27, but he quit after that (possibly because so many of us were laughing at him at work for losing so much money). He was the type of guy that would hold a stock to zero, but I'm sure he got margin called before that.
There is no Credit Card that offers 0% rate on late payments. And most credit card users are late (very late on their payments).