The Mini actually had an obvious user base though, kids/teens (including mine) and those who don't like/want/need a massive screen on a bulky phone that won't fit in their pocket. It might not be the majority, but it's more than a small niche.
Unlike the Plus which is now obsolete, there is still a market for a capably-spec'd or even Pro-level iPhone Mini. Sadly, the beancounters are in charge and they aren't smart enough to realise that market trends, as spouted by their beloved market research firms, aren't always reliable and customers are fickle. Apple are just another quantitative company these days, when they used to be all about the qualitative.