You can have a digital goods marketplace where you do use LN on SN, but for something that needs in-person delivery, I can see this being very useful. Heck, there are plenty of people that want to trade cash for BTC or vice versa, so that alone would probably be a big value-add.

A marketplace without allowing users to send payments to each other on SN feels like a missed opportunity, *but* it would allow us to not have to escrow and deal with order status stuff.