UB - families with 2 kids or in-laws, etc. regularly purchase cars with 3rd. row seating. There's a HUGE market for the same. CX-9 I have ridden and find it price wise comparable to any other SUV offering 3rd. row seating. Next, interiors are superb and overall handling/dynamics are better than ANY JP/EU and MOST US brand SUV offering 3rd. row seating. Let's not compare CX9 with LUXURY brands though.
Now, at the same time I do understand such families opt for vans like Sienna/Odyssey as it offers more trunk space than SUVs having 3rd. row seating. I am not comparing those vans with CX-9. In it's segment its a really solid offering at a very competitive price point.
The only reason I can think of - as to why sales are low is lack of marketing, lack of user knowledge and finally lack of Mazda offering a van like car with 3rd. row seating.
The CX-9 is a fine vehicle, but its strong points aren't high on the list of priorities for most families shopping for 7-seat vehicles. It looks good, has a classy interior, has a well-balanced semi-sporty suspension, turns well for the segment, provides some feedback from the tires, has great low-end torque and midrange, a responsive transmission, and it's quiet. The problem is that a lot of people shopping for a mainstream three-row family hauler don't care about any of that. They care about child seat fitment, perceived safety and reliability, ease of getting their kids and stuff in and out, whether the dog can fit behind the third row, etc. In those areas, the CX-9 doesn't rate so well. There are also people who just want a taller vehicle with a more utilitarian SUV-like look.
FWIW, my wife and I did compare minivans to the CX-9. Perhaps we are rare in doing so. We considered every vehicle under $50k with three rows of seating, and drove most of them. Our choice came down to the Chrysler Pacifica Limited vs. CX-9 Signature. Why? From my wife's perspective, they were the most car-like to drive and had the nicest interiors. From my perspective, they could both go around corners pretty well. I really had no interest at all in a minivan after driving the Odyssey and Sienna, but I was impressed with the Pacifica. And I'm not joking about going around corners. The Pacifica doesn't give you as much feedback as the CX-9, but it can be driven just as fast or faster. On a vacation in Vermont last summer, I took the van through the Appalachian Gap (VT-17) and walked away from a Miata that was trying to follow me. I did cook the tires in the process and had to listen to my wife b**** about the smell afterward, but I had fun. Most minivan buyers aren't going to do anything like that, but it's nice that the designers cared enough to give it a fully independent suspension and worked to minimize body roll and understeer. The CX-9 was a bit better to drive, but it wasn't so much better that we could ignore the practicality of the van.
I know so many people that bought their cars for the wrong reason. It's frustrating to see it.
I mean, how do you explain people buying cars like a Chrysler 200, or a Jeep Compass, or the like?
Chrysler 200: AWD, big V6, nice interior, big discounts.
Jeep Compass: A compact SUV that can actually go off-road, but with modern crossover styling
Downside of both: FCA quality