In January this year they reported that they were getting 1 million new customers per month and that overseas revenues are now exceeding domestic revenues.  With the kind of market penetration they now have in many countries (their operations are still very restricted in some), small merchants who don't accept PP as a payment method are at a disadvantage.  The balance has tipped towards demand for PP being customer driven whereas in the past it was often merchant imposed.

The sheer amount of money they turn over requires that they act more like conventional aquirers/payment processors.  When you're dealing with billions, being able to cut losses by even a fraction of a percent gives you a significant advantage over your competitors.  PP mightn't quite be at the stage of using predictive analytics to profile its customers from their first transaction, but it's almost certainly running some sophisticated anti-fraud and AML algorithms to identify high risk accounts.