People are lazy, people are continuously keeping their coins on exchanges regardless of endless warnings (there were 2 million Bitcoins on Coinbase some time ago)

In the far future probably both centralized exchanges and banks (their competitors then) - will provide their branded custodial lightning wallets for Average Joe. And running lightning node & opening/closing channels will be their duty (and of course they will be able to afford it regardless of L1 fees)

Yes, that will be unfortunately step towards centralization, but caused strictly by the demands of human laziness... (change my mind ;)