They did already. In fact, a silk road plugin for lnbits was the genesis of Nostr.

nostr:npub1market6g3zl4mxwx5ugw56hfg0f7dy7jnnw8t380788mvdyrnwuqgep7hd

It's a good question, tbf.

I've already bought weed from nostr listing on Amethyst 🤷‍♂️

👋 gm we are a foss bitcoin marketplace , not silkroad. You are to list products on our site or download and install your own instance on your server and list and sell what you want. 🤝