The problem is there aren't enough people buying mini phones to make it worthwhile to Apple. But that's only if they keep a mini around permanently.

However if Apple released a new iPhone mini model every fourth year, I'd wager these would be like a McRib-style smash hit sales event, compressing the comparatively small mini-enthusiast audience into a time-limited buying window. It would also trigger FOMO at a time when many people are increasingly willing to delay upgrades for 5+ years.