people use dollars for the exact same thing; i dont think the neighborhood weed dealer is really going to ask for bitcoin over a good 20 dollar (or whatever currency you use) bill. same thing with larger deals, in fact, its probably much harder to trace a suitcase full of paper money (assuming there isnt a tracer on it or anything) over a pseudoanonymous transaction made with bitcoin. there is no possible way to trace that suitcase, aside from reading individual serial numbers of the bills, and even then you would have to know what serial numbers are contained in that suitcase full of money. with bitcoin, the transaction is right there o the network for everyone to see. you would know exactly which address sent exactly how much money to another exact address. its just a matter of linking those addresses to a person and the transaction to what deal was made.