You will want to discuss this with
@CapriRacer but typically, shoulder wear happens on steer tires even when they are properly inflated. Toe has the biggest impact on wear, and so suspension geometry and configuration are key drivers here, and they are tuned for things other than long tire life.
Even tire wear is not the primary goal of the pressure spec. The tire must meet the load carrying capacity of the vehicle, and on top of that, handling and predictable emergency maneuver performance along with traction and ride quality are all taken into account.
Toyota engineers aren't stupid and the placard pressure was arrived at based on the above. They've compromised wear performance in order to achieve better performance in those other areas. We've had this discussion before due to the same complaint on other vehicles.
Note that I'm not trying to be dismissive of your concerns about this phenomenon. I completely understand being frustrated at what appears to be a bizarre oversight by Toyota at first blush. However, once you understand that wear performance wasn't top of the their priority list, what you observe in use ends up making more sense. When you try and counteract that by increasing pressure, you are effectively creating compromises in these other aforementioned areas that may not be immediately, or even at all, obvious.
There are some historical posts made by Barry in previous threads, but hopefully he'll chime-in here.
