Most people in my cohort aren't exactly destitute. Certainly, a business could make money selling to teenagers. They just couldn't achieve the volume that something like Facebook has.
Generally, people like free things and have a disregard for their privacy, (myself included) which is why ads are far more lucrative.
HOWEVER: This observation is not necessarily reflective of the generation at large, so I would take this with a grain of salt.
See this UK account for 11 to 18 year olds which allows a debit card.
(http://www.rbs.co.uk/personal/current-accounts/g1/young/revo...)
HSBC give you a savings account when you're seven, and add a current account when you're 11, with a VISA debit card.
(https://www.hsbc.co.uk/1/2/current-accounts/under-18-bank-ac...)
US banks love overage fees (making credit card interest rates an amazing bargain). Plus there is the liability of checks/ACH which can cause overdrafts.