[pekk]

Any old server gives you full flexibility. One key point is, what do you mean by secure? If they give this Turing-complete machine to their customers, and then the customer uses or is given the wrong software (Murphy's Law), how is it going to be assured that this is still "secure"? And are many other paying customers looking for this Turing-complete thing they can write their own software for, or don't a lot more customers want turnkey solutions to specific problems?

[danpalmer]

While these devices are turing complete machines under the hood, the interface to them is incredibly strict.

Using them from code is like using a remote API, you can't execute code, you can only make requests and receive responses, and a lot of thought it put into the interface to ensure it's as secure as possible.

As far as the physical interface, they are more like an appliance than a server, in that you don't get the normal ports you would on any other machine, the actual casing is typically alarmed so that keys are wiped when the device is opened, important circuitry is embedded in epoxy so that it's essentially impossible to attach debugging instruments without destroying it, etc.

I can't really emphasise enough how these machines are designed for security.