It makes sense for BTC to attempt a mix of both on and off-chain ideas if other forks are going to keep their focus purely on-chain. Why put all your eggs in one basket if you don't need to?
Don't forget that the Lightning Network could be also used for cross-chain atomic swaps. In some cases, it still does not make any sense, but it's a feature that might be used by people who want to avoid using exchanges and escrow. Some people think that Litecoin and the Lightning Network is a perfect combination. Well, payments processors are busy implementing Bitcoin LN payments.