Raison d'etre of the Voynich?

[ReneZ]

What are the most plausible theories that could explain the purpose of the Voynich manuscript, and what evidence supports each of them?

I like the second part of the question, and I am much more curious about that part.
I think that one would have to allow a wide scope of possible 'purposes', covering also: 'no useful purpose'.
(And of course 'useful' is subjective).

Encrypted (or otherwise obfuscated) meaningful information is just one general category.
Supporting evidence: not a lot. This is something that was done, but only very rarely on long texts.
Contradicting evidence:
1) we can't decipher it, and this should have been relatively straightforward for an encrypted text
2) the general appearance of the writing is not that of an encrypted text