All models with a hybrid version

Toyota partnered with Ford on developing a rear wheel drive system that would work for trucks. When it comes to tow ratings, and possibly payload, the current hybrid systems available don't measure up to where the manufacturers are willing to put a stake on it. The Prius has a zero tow rating. So does the FWD RX/Highlander, a SUV that is expected to be able to do things like tow. To tow 3500lbs, you have to get the AWD. The traditional ICE version, with the same displacement engine is rated 5000lbs, and IIRC, AWD isn't a requirement.

That's why you don't see a hybrid Tacoma yet.

Now that they have an improved system in the Camry and the Avalon, the minivan shouldn't be far off. A minivan is bigger and heavier than a car. Earlier generations of HSD might not have provided enough of an improvement to justify the cost.

 

Interesting that Toyota Australia actually "pushed" for a towable Camry Hybrid and they delivered, although the rating is only a mere 300kg braked/unbraked. One of the reasons for low such a low rating is that reversing will only be in electric mode.

But at least it could tow now to compete with the other Australian made cars.

Galaxy Nexus ? 2

 

Yep. The Highlander is FWD unibody. The Tacoma a RWD full frame. The ICE orientation is different by 90degrees. The HiHy HSD with V6 might not fit in the Tacoma engine bay once rotated. Toyota might be able to adapt the RWD hybrid system that is in one of the Lexus for the Tacoma.

Another issue is the market. The Tacoma is lighter, but has worse aero, a hybrid version will probably have the same combined as the HiHy. With advances in ICE and transmission technology, full trucks are getting better fuel economy. While not hybrid good, they are better rated for work. Depending on how Toyota equips a hypothetical hybrid Tacoma(the HiHy is pricey), the competitors will cost less.

I hadn't considered the electric only reverse. A trailer plus a low SOC might leave the vehicle stuck briefly if it had to reverse. Seeing how sensitive the traction control was on my 2005 Prius, I was thinking Toyota was worried that the decreased weight on the front axle from a trailer could lead to more traction control events. That might lead to collisions. Whatever it is, Toyota has a reason for a low to none tow rating. People here have been towing with the Prius regularly without have problems I've seen reported.

The American market is denied tow ratings for cars in general. The Sonic is rated zero here, but is rated 500kg unbraked overseas. It's not a major reason, but contributes the number of trucks and SUVs on our roads.