Your mileage may vary, but I think that in many niches the portion of users you have who refuse to use Paypal/GC is small enough that spending engineering resources to integrate more payment options is not profit-maximizing compared to spending the same resources to just get more users.<p>Anecdote: in three years I've had six inquiries about alternate payment methods and <i>all</i> of them were because "I don't or can't pay online".