The tablet also has more educational value as it supports handwriting and drawing, though it comes at the cost of not being pocket-size (adding inconvenience for users who just want to listen to music).
Mini has the small bezels, USB-C port, supports the magnetically charged stylus, and has an A15 with 4 GB RAM, so it's priced more in line with the iPad Air even though it's the small one.
I used to have an iPad Mini, I think 3? Whichever model was before it got Touch ID. Back then it was a smaller and cheaper version of the normal iPad, more recently it's moved to the middle of the line (but below the "Pro" versions).
I think what I had was a 2 purchased after the 3 came out, someplace was clearing them out for around $150 off even though it was practically the same device except it took half a second longer to unlock. Pretty good deal, eventually got demoted to kitchen recipe screen.
I think the iPad Mini makes sense as a product line in general. Which is being a smaller screen (and thus cheaper) iPad Air. It does work as an option, but so do iPads.