I might still have been interested in a smaller iPhone to bring on runs with me once upon a time (eg: back when I was using runkeeper to map my runs), but an Apple Watch pretty much covers that for me now.(There are social factors to this. For example, I imagine minis are only interesting to men, because women wouldn't have sufficient pants/dress pockets regardless. They use a purse either way. So that advantage of the mini already goes away for ~half the population.
I really do like the size and the weight of the 13 mini, but ultimately, the batter life and the screen size of the 13 pro max won out, though I still prefer the 8+ form factor best. It's just comforting knowing that your phone has ample juice to make it through a full day no matter what you throw at it. I have even stopped bringing power banks out with me these days.