Fees are super low (~1 sat/vbyte ~0.15 USD) LN works so well people are getting worried about the "security budget" (fees are so low, miners may die in far future when there is no subsidy) On-chan scalability does not work for very many reasons. Just one example: imagine the bip110 situation if Bitcoin had 100mb blocks. Fees would be even lower then now and it would be super cheap to stuff the chain full with jpegs. Luke wants to even decrease block size.