Actually the problem is that people will only adopt technologies they understand. You shouldn't compare yourself who has spent thousands of hours understanding all these complex terms. Leave the Lightning Network for a moment; Try convincing a merchant to adopt a highly volatile currency that works autonomously, with no support to help him. Now explain him why should he do that. Visa and and generally credit/debit cards are far more convenient to use, even if they're working centralizedly.

Not all people appreciate decentralization and that's justified.