OH, please don't tell me I'm not preaching to the CHIOR!
My first horses were riding horses, and I still have a riding horse. I love him very much.................... yet which horses do I really do something with more? It's our minis! My big horse does drive, and is the first driving horse I owned, however, minis are so much easier to hook up.
An average size mini in reasonable shape can pull two (2) adults in a well balanced cart. I have plenty of friends who'd like to do a "horsey" something, but that may not include riding. Even H, for ALL his years of helping me take care of horses DOES NOT know how to ride. He may think he does, but in the saddle, his ground pointing toes tell me otherwise!
You can sit in a cart and drive a horse with a friend how isn't at all horse knowledgeble, but still wants to have a horse experience, and be safe because YOU know horses and how to drive. Plus, I've been on more than few trail rides and how easy is it to hold a converssation? NOT easy, at least in my exprience. However, side by side in a cart, you can hear what each other has to say.
Miniatures are at the high end of the ruler when it comes to horse smarts. That makes them not only fun to drive (and train to drive) but also all of that in hand fun you can have with them.
I've been around lots of horse women, and I'd bet "the farm" that more than half of them are honestly afraid to get up on top of their big horses, so one thing "minis are good for" is to teach confidence... and in the process, have a lot of fun and maybe arive at new hobbies and spirations (driving and in hand performance).
I started out owning big horses and still have one. I remember when we got our first mini, I figured we'd really love him and enjoy taking care of him, but I didn't think we'd enjoy him as much as we did our big horses... NEARLY 15 years later, and not too far in, we came to honestly enjoy our minis MORE than our biggies.
We love to take care of animals, we have loved to breed superior x superior and raise the results, and driving is an absolute blast and sharable in a way that riding is really not.
Minis are usually extremely smart and very people oriented. They are "good for" so much, including sharing with others. Honestly, minis are the breed that nearly everyone can experience.