Ultimately, Lightning can provide instant transactions for low value, frequent purchases at brick-and-mortar stores. The costs of merchant integration aren't justified yet until LN adoption is much more widespread. The same was true of credit cards at one point too.
In the meantime, there are apps like SPEDN that merchants can integrate with existing POS terminals. SPEDN uses Gemini to custody cryptocurrency so that merchants can accept it without requiring confirmations.
While I think that lightning has real use, I think it has yet to overcome at least part of its ailments. Bitcoin as a whole has gotten better and better at handling volume, just on the 27th this month we hit 369k transactions which is similar to the usual transactions you'd see daily back in Dec 2017, but without the excessive fees and long wait times to clear.
Although slightly Off Topic, Localbitcoins volume has dropped to lower than it was back in 2013, I guess it says a lot of the emerging platforms that people are jumping over to, all of these platforms in a way alleviate the burden on the mainnet. But maybe I'm just seeing things wrong