Carrying stuff in the car and towing stuff are two different things. Vehicles are rated for how much they can carry (sort of) and (sometimes) how much they can tow. Not all vehicles are rated for towing, as you've found out.
Rather than looking at towing capacity, I think the better angle is to look at total cargo volume, cargo area shape (for ease of storing a variety of items), and ease of loading and unloading the cargo area. These are a better comparison for SUV vs. sedan/wagon/minivan, while towing capacity is better when considering pickup trucks.
The mother with 2+ kids involved in a couple of sports might find herself asked to take kids and teammates, with their gear, to a variety of places a good deal of the time. That will use a lot of cargo volume, but not very much weight. Rather than trying to convince her she can tow it in a Corolla, try to convince her that a station wagon or minivan can carry all of that more safely while still not being "uncool." Yes, the "coolness" of the vehicle plays a large part for many people who buy SUVs, and many are horribly ignorant, yet defiant about, the safety concerns.