There is a reason the military doesn't paint their tanks bright pink... Armor is important, but if you don't get shot at in the first place, even better.
Security by obscurity is not painting tanks in camo. Security by obscurity is assuming your enemy won't find your tanks because you didn't broadcast on public radio where your tanks are.
That is another appropriate analogy (and it's why the military invests in SIGINT).
To the point though, no one should "assume the tanks won't be found", but it's still worthwhile to do things to make it less likely they will be found.
In military parlance, this is the distinguish between cover and concealment. In practice, good cover often provides some degree of concealment, but on a purely theoretical level, the two are orthogonal.
