That's because most P2P exchanges are centralized. It's easy enough to regulate something that's controlled by a single entity. But when you try to regulate something decentralized, you'll eventually fail in the long run. The is because there's no one you could hold accountable for their actions. Considering that governments don't have jurisdiction on every region of the world, the efforts of trying to regulate decentralized exchanges become in vain.

I believe that the same thing will happen with Bitcoin and other cryptocurrencies on the market today. Yellen's comments are all about scaring people from using Bitcoin on the top the US dollar. That's normal, since the government doesn't want to lose control over the mainstream economy. We should expect constant opposition to Bitcoin and other decentralized cryptocurrencies in the future. One thing for sure is that it will be easy enough to implement KYC/AML laws on centralized exchanges. But on decentralized exchanges, that's another story. And don't let me get started on in-person trading, and off-chain transactions. Eventually, governments will face the fact that it's impossible to regulate Bitcoin. It's too late for them to put an end to the revolution. If they would've wanted to stop Bitcoin, they should've done it in its early days. Now it's a matter of joining the Blockchain revolution or get left behind in the dust. Just my thoughts