Not necessarily.

For the starter, quite some posters mentioned they had to either close some of their existing Chase cards, or re-allocate their existing credit lines in order to open the BA cards - this tells you right there that many customers are EXISTING Chase customers.

In today's economy, it would be rather foolish to say the airlines trump the banks (though the banks only triumph because they get government money. But that is another story.)

As you also know very well, one does not have to redeem the miles on BA metal - quite the contrary, BA would have to shell out some bucks to pay for the partner airlines seats.

Dont forget most folks in US are NOT accustom to the horrendous fuel surcharges BA imposes on the Brits. So most would redeem their miles on partners who either have a much more reasonable fuel surcharge or does not have fuel surcharge at all.