They just don't care such problem.
they want LN to solve this, but people don't really need LN, if they have other currency to pay the coffee with low fee.
Amen.
LN is banking all over. But the niche is taken by fiat banks. LN just brings in extra hassle. Crypto, needing to be censorship resistant, trustless, decentralized etc.... has a huge burden in comparison with a centralized fiat bank ; that burden needs to be offset by an advantage in order to be competitive. When there were 20 transactions a day, it seemed naively that this burden didn't really exist. Click, and 10 minutes later, $10, or $100 000, was securely on the other side of the world. The growth was financing the inflation and the PoW, everything was still small-scale, so it seemed simple, "if only everybody used it".
No, the needs for censorship resistance, trustlessness, security, decentralization etc... are big resource hogs, and in order for it to be competitive with fiat banking, it has to bring in something that you cannot do or cannot do as well with fiat banking.
So crypto will always be a niche applications for those things you cannot do with fiat: everything which is illegal, lawless, unregulated, or where a good legal system doesn't exist, in those cases where the legal system is too corrupt, or when international situations make the connection between several legal systems too difficult.
And coffee buying is none of them.
Bitcoin is costing about $400 million a year in PoW only. Add to that all the network and computing infrastructure, and you see that bitcoin, as a payment system allowing for 3 transactions a second, is not cheap. It costs about $4 a transaction. This is now compensated still by inflation which is not seen because of growth (greater fool growth), but the real cost is there. You need to have a niche where a transaction is worth $4 as a competitive edge in order to do so.