My point is that : The core problem is not if the transaction cost is big or small, it's about bringing blockchain into mainstream.
For example, you gave your grandma a game account to play a game on Ethereum, and every actions need to use smart contract.
But she doesn't have ETH because she know nothing about blockchain, so she can never play the game unless she learns how to buy ETH on exchange, how to use wallet etc.
But with an account which dosen't require transaction, she can use DAPP without any knowledge about blockchain.
It's all about an user friendly front end. Bank transfers have fees, pretty high compared to crypto. Bitcoin is still cheap compared to most bank transfers and faster. Yet we see old people using bank transfers all the time because they are used to their front end.
As far as grandmas using Bitcoin, I don't think it will ever happen, until current generation of millennial are old since they will grow up with Bitcoin.
LN will have very user friendly front ends which anyone can use with a phone. The average Joe doesn't need to know what even an on-chain or off-chain transaction is or even the fee since it will be tiny. All that matters is it will be easy to use and transactions are settled in the Bitcoin blockchain which is safer than anything else out there.