I answer a lot of questions on Quora. Many of those questions are about automotive things that may be of interest to CarNewsCafe readers. Like this one.
My Answer: Three things: cost, maintenance, and questions about efficacy.
Starting with the first point, the catch can adds cost to the car’s design and build. It has to prove itself worth that cost if it’s to be added.
The second point is maintenance. Adding another point of maintenance to the vehicle for the owner to have to worry about is generally not a selling point. If it weren’t, there’d be a lot more diesel-powered cars on American roads than there are. Having to add urea and learning that oil changes are often far more expensive puts people off.
The third point is efficacy and ties into the other two because if it’s not worth it, manufacturers aren’t going to add it. The only real testing that’s been done with scientific backing is that done by the SAE. Their test, however, involved a very high-mileage vehicle and only that one vehicle. That’s far from conclusive.