Now, Mobius, while I do understand where you cumming from, in my point of view the Chastity Belt, even thought it was constructed as a method of protection (from rapes), and later enforced as a method of prevention (of adultery) is all about enforcing will of the owner over his property.
Now, as you kindly pointed out – it was designed (sort of) to keep things out of those wholes, but, as long as it is locked on by the Master, who are we to judge how is He/She enforcing the chastity on the owned subject?
I fell that by being locked in a device like that, that is preventing me from doing what and when I want is constant reminder who is the Boss, now if the Boss wants me to be empty or full – it truly is up to him. Chastity is part where you don’t get to be happily humping someone else – the probes don’t count!