A security module or a key fob/smart card processes the key internally using its own dedicated ram and cpu without any debugging support. This way, even something will full ram and cpu access or a compromise of your machine, there is no way to export or access the key. Data is passed to the module and it returns the scrambled or unscrambled result based on the key which no body knows or has ever seen. A key locked with no way to access can’t be hacked without physically stealing the module, which is where your pin comes in to save you. The TPM is a very important part of a secure boot chain. If you want to secure other things I wouldn’t blame you for using a separate module or fob that isn’t always connected util it’s actually needed and it should only be activated with a physical button or something so you have to be present to engage with it. This adds even more security. So you could use the TPM for boot chain security and a separate fob or data privacy for example.