To pogranicze, ponieważ do obcych zwracamy się per Pan i Pani, a tu chcemy się zwrócić "po prostu", bezpośrednio, niemniej zachowując podstawy kultury, lub zachowując podstawy twarzy.
It's a way to be politely correct, but indicating either disrespect or a human relation approach.
Compare English "mister" "Hey, mister!" "E, Panie!".
It's word and culture play.
You either want to be polite, keeping your "face" (So nobody can, correctly, call you out as rude, for dropping the Mr/Mrs and avoiding eventual embarrassment "e, ale na Ty to my nie jesteśmy" - "Hey, we're not per "you" basis".) but showing the person is no higher than you in hierarchy and therefore addressing per "you", sort of - chodź Pan, weź Pan - chodź, weź being "you" addressed.
Now the reason for this can be impoliteness, but more often, just a levelling, with maintaining the remoteness of sir/lady address.
So the guy wants to level with you, but he's not your friend or doesn't directly intend to be one, capice?
Sir knows it's worth doing so - Pan wie że tak jest warto zrobić
Ey, mister, you know how it is - Sam Pan wiesz jak jest