They offer the worst currency conversion rate imaginable when you go to withdraw to your non-US bank, so some people prefer to keep it in PP as a USD spending account i guess.
True, if I have to pay in a foreign currency I let Paypal charge my cc in that currency, so that the cc company converts my currency instead of Paypal.
I don't recall the difference, but I believe the cc company gave me more than an order of magninude tighter spread on the conversion, perhaps even two.