They could add a lightning invoice.
They are working on adding it. It will be available soon enough. There are posts that nostr:npub1sg6plzptd64u62a878hep2kev88swjh3tw00gjsfl8f237lmu63q0uf63m has made about this in the past. The point is to make it successful and easy. No point in adding it if it’s a hassle for new users.
Discussion
I totally agree with you, I’m just relaying their statement about it. It would change a lot of things for Bitcoin if it became a daily decision at every payment checkout. Im not a technical enough to know how difficult it would be to add, but it doesn’t seem to difficult.