The PR2 was a household robot developed by Willow Garage and sold for 400000 US$ each. The fact to know is, that the robot was a complete failure. The amount of sold devices was low and the customer doesn't see an advantage in using the robot. This failure is surprising because the idea was to use the device as a household robot, for factory automation and for office automation. How can it be, that a robot is technically state of the art but the device can't be utilized for practical applications?
The short explanation is, that using a robot in the real life is equal to utilize the robot as a tool. A tool is a device which can fulfill a task with a high productivity. This social role can't be played by robots, especially not by robot who are very advanced. In contrast, there is a different purpose in which the PR2 robot works great. In synthetic robot challenges and testing out new AI algorithm, the PR2 was the most succesful robot ever built. Many academic papers were published around PR2 projects and it helped researchers very well to become familiar with motion planning problems.
To answer the initial question why the PR2 was a commercial failure we have to define the difference between a tool and a robot. A tool has a low automation level, in most cases it's a mechanical machine for example a bicycle or a hammer. And if the tool is equipped with electronics for example in a fork-lift-truck, the amount of electronics is low.
In contrast, robots and especially human like robots are at first computers in which the hardware plays only a minor role. The PR2 robot was some kind of supercomputer built into moving cart. It was working with the Linux operating system and was equipped with many sensors. This makes it a great platform for software engineers but it's not longer a mechanical tool which can be utilized for practical applications.
A robot is an example for an overengineered tool. The idea is to upgrade plain mechanical tools with lots of computing power and sensors in the hope that the overall performance will become better. The opposite is the case. A useful tool, doesn't contains an onboard CPU and it can't be programmed in C++. The most advanced sorts of tools which can be used for practical applications are CNC machines. These machines have some features of a computer, but mostly they are not computers but numerical controlled machines. Sometimes a CNC is rejected as to complicated because of this reason, but other CNC machines are working fine for practical application. It's not possible to upgrade a CNC machine with more computing power into the direction of a robot. This would make the machine useless for practical applications.
Broader context
To understand why the PR2 robot project has failed we have to describe the overall idea why the robot was realized. For doing so we have to go back into the mid 1970s. In that decade certain technology was available for example electronic refrigerator, automated washing machine, cars and desktop calculator. From the perspective of the 1970s the hope was to invent new sort of machines which can increase the technology level further. And the perfect candidate is an household robot which is able to open the existing refrigerator and is able to clean plates.
The story about future robotics was told under the name “fifth generation computer”. That was technology not available in the 1970s which includes robots and artificial intelligence. The PR2 robot was a typical example of a fifth generation computer project. The idea was to realize the wishes of the 1970s. The question is not why the concrete PR2 model has failed, but the more general problem is why Fifth generation computers aren't build yet. What we can see is, that up to the 1970s the technology has made linear progress, and then the development stopped. It's not possible to automate a household or a factory above the level of the mid 1970s. The normal kitchen in the year 2019 looks the same like a kitchen in the 1970s. That means, apart from the normal household machines no further technology is available. The logical next step after a vacuum cleaner and a refrigerator would be a household robot and from a technical perspective the PR2 model fulfill all the requirements. The unsolved issue is how to use the machine in a meaningful way. It seems, that the software programmed for the PR2 doesn't fulfill the external requirements. That means, the program under with the robot operates is working with a different principle than expected.
A possible explanation why automation has limits is given by Wikipedia https://en.wikipedia.org/wiki/Automation#Limitations_to_automation If a process gets automated there is less labor available which can be automated next. Colloquial spoken the remaining manual work which is needed in a modern kitchen is low, so it makes no sense to use robots for that work. The remaining non-automated processes was reduced by technology which is already available.