Isn't that because they don't have a more effective alternative? They're forced to rely on the security by obscurity of camo (ignoring the guns).
If you had an indestructable soldier, you could paint them bright pink and have them live stream their position, it wouldn't matter they're indestructable.
Isn't that true for software too though? You cannot ever rely 100% on any tool you use, so if you're serious about actually avoiding penetrations and not just about the academic discussion, you're better off using at least a bit of obscurity on top of your real security system.
If you had an indestructable soldier, you could paint them bright pink and have them live stream their position, it wouldn't matter they're indestructable.