Yes, most do already. Some still use on chain but then your order isn’t completely until a tx has enough confirmations.

Back in the early days of Bitcoin there were a number of ecommerce sites that started taking on chain Bitcoin payments because there was no lightning. I had bought stuff off of Newegg with Bitcoin before. But a lot of them stopped taking Bitcoin at all. Not sure why. Lightning would definitely be better for smaller things. If I was selling high-cost items I would prefer to take on-chain payments.

They built it already nostr market.. they announced it earlier today..