I don't think that it is accurate to say predatory lending laws prevent cards from being LEGAL. They may have prevented them from being profitable enough to grow beyond the upper/upper-middle classes. Amex, Carte Blanche and Diner's club were created in the 1950's.
Having a credit card and using it wisely is an important and vital skill to have - paying off in full each month to get a cut of the interbank fee just makes sense. And if you are really careful taking advantage of interest free / other special offers can really pay off too.
Just because mortgage interest is tax deductible does not mean that you should not pay off your mortgage. No matter how much interest you pay when you deduct it you will only get back a PORTION of it so you are still net out of pocket in almost all situations. When you start taking into account "real" interest rates and rates of inflation then sometimes your advice might make sense. That said, I do have a mortgage and its nice to see the deduction but I am still paying a lot more in interest than it is saving me on my taxes.