"These days" that wasn't the case four years ago when they arbitrarily took it away. How would you know what the level of demand is? I would selectively purchase a phone with a headphone jack over one without, but that demand is meaningless without an option. Apple led the pack with the highest R&D budget of them all, with a premium smartphone. They, uniquely, took the headphone jack away while launching airpods.

You're right about there being no mystery there.