I once explained Credit Cards to someone like this. It's like having a rich uncle & you get to decide if he is going to leave you money or leave you bills to pay. Properly used, credit cards are great. Improperly used & they will ruin you (like your friend). I look at them as saving me time & money. I save time by charging everything I buy, no writing of a bunch of checks, No running to the bank for money, just charge it. By doing that I save my time & I get to use someone else's money for around 30 days for FREE. A short term loan that I don't pay interest on. And as the cherry on top I make (rewards credit card) for every dollar I spend I get a penny back. A penny isn't much BUT if it's on every single dollar you spend it adds up. I literally have no reoccurring bills that don't go on my credit card & I write one check a month to pay it off.
So why do cc companies pay 1% back? It's simple, some people can not handle cc's wisely. They do exactly what your friend did. And those people pay a LOT of interest over their lifetimes. If a person falls into that category they should never ever use credit cards.
I found that if I carry cash I will spend it. Two bucks for a coke, hey I'm thirsty & how about a candy bar to go with it? Five bucks gone for nothing of value. I just realized that I "blew" cash when I carried it so for 30 year I almost never had more than 3 dollars in my wallet. Now days it doesn't matter that much so I might have a 20 in there.