This goes against other goals such as a longer lifetime for the product by being able to upgrade / replace the RAM.
What is your assumed attack?
- The computer is powered on, booted and then stolen?
- The computer is in standby and then stolen?
- The computer is hibernated and then stolen?
- The computer is shutdown and then stolen?
I would think that the mitigation for the third and fourth is to clear the key from RAM at the appropriate point in time during shutdown.