Many of the measures that provide effective physical security also make a device really unsuited for personal usage. Look at HSMs for an example of this. And even they rely on being stored in a physically secure room and protected from theft.
It's a matter of being more determined than your attacker. Imagine a device that will irretrievably brick itself if tilted more than a certain angle, if left unpowered for more than a certain time, etc. and that has to be under constant guard. This seems almost incompatible with any kind of personal use. And some measures may only work in one instance, with the attacker planning for them the second time they have an operation.
Many attackers also don't have the same restrictions the police has. In the Ulbricht case the police may have been forced to use a device that copies the data with no human intervention just to preserve the chain of evidence and not have suspicions that the agent operating the laptop altered it while installing additional software. An attacker operating in the grey/dark area might just immobilize the user, snip the wrist cable, and then retrieve the necessary data either directly at the console or by siphoning it via the network. Or the police may just start video recording in great detail every step from the moment an agent touched the laptop until the data was exfiltrated to remove suspicions of tampering.
But such a tool would be of great effect against an undetermined, unsophisticated attacker committing a crime of opportunity.