*Secure* randomness

The question isn't really whether we have an ideal rng that produces non-patterned output—the question is whether our rng produces random output suited to operational demands. So we do in fact "restrict" randomness in order to get non-patterned output that is also not value-repetitive.

If all we want is pure randomness, and we don't rely on it for anything, any non-patterned output, however often it may reproduce specific values in its output, is sufficient. A d6, for example, or a coin.

But if what we want is *secure* randomness over long cycles, then repeating entries is bad. Collisions are breaches waiting to happen. Even if the sequence doesn't repeat, if I know enough of the output, I can wait.

Strings of 1s may happen with a two-state generator, for example, but the point of running them through much more complicated chains, to generate "more" randomness, is really also to generate more *usefully secure sequences* (that is, non-repetitive) of random numbers. Which is why also the filtering and throttling and whatnot.