I wouldn't be so quick to judge. What if you are the one who doesn't understand? It's just a conversation, leave the door open that you might learn something too.

You are correct that there is an audit trail, but it's somewhat anonymous. Every time I get paid, I can generate a new BTC address, and I have a new chunk of money that's potentially anonymous. Unless the person who paid me spills the beans, no one knows that I have that money, and even if you could figure out what that money was spent on, you still wouldn't be able to connect it back to me, without the help of the person who paid me.

You could also use some sort of network/behavior analysis to guess who was using the money, but that's far from "trivial". And it requires that you already know who is behind quite a large percentage of transactions, so there's a bit of a bootstrapping problem.