I mean, really, why would it be encrypted?

[Mark Knowles]

We know it's not a common European language in a simple code - luckily there is some consensus on this.
We also suspect that a very complex code is anachronistic.

So indeed, you could ask, why?

But all other options also raise questions. If it's nonsense, why on earth write so much? Q20 would have been entirely unnecessary.

I think you highlight an important point, namely that the Voynich is an anomaly. Whatever the explanation for its existence it will still inevitably be incongruous.