I didn't ask for them. I have 4 total. Two when I got when I was first starting out. I have two cards which comprise the bulk of my credit (one from American Express and the other Chase), which represent ~50% of that $90k. Both have credit limits around $20-25k.

>but I'm wondering why would anyone want to use their high-interest credit card to borrow even a few tens of thousands?

I don't know, but I'm sure as heck not going to utilize them that much! I am sure the credit issuers wish I did though.