One American's opinion. I'm in my early 20s and in good financial standing, I have 3 credit cards with airline miles programs. Using them means for the past year I've used a free flight every 3rd flight, and my girlfriend and I will be traveling to Europe RT for $1200 for 2 tickets. I fly a lot, and it's saved me a couple hundred dollars to have a few credit cards, and the inconvenience of keeping < 5% balance on each.

I'd imagine it's because the credit card companies have less restrictions on what they can do here compared to Europe, so they can afford more extravagant offerings.