I like when they don't pay....gives me something to blow up....
Anyways, I also don't consider my main pirate char a big money maker, and don't log into my pirate expecting to make any significant money (although the occasional unprotected gold convoy is a different story). I have a trader and miner char to feed other chars money.
I pirate for the interactions....piracy really doesn't pay that well, and pirates who try to make a living to support their entire account are the ones who demand 20 mills from a camara and give the rest of us a bad name.
Pirate for the rp interaction, not for the cash....that's my opinion anyways.
EDIT: Hmmm, might want to actually answer the question of OP, yes?
I ramble when I drink....anyways, I think piracy would probably become more frequent, and also far more boring, if every trader automatically paid up....the fun of being a pirate is doing the bad stuff, and a big part of that bad stuff is making silent/defiant traders pay for their shortsightedness and disregard for my ability to deliver delicious
SNAC's....muahahahaha.