Hi Bruno,
The wooden case makes the melodica look great. As soon as you put a nice looking wooden case on a melodica, it create a perception that elevates the instrument to a new level.
Not to mention that the sound from the wooden-cased melodica was noticeably sweet and smooth.
Imagine if melodica makers created a beautiful wooden cabinet and then sold several types of the innards that you just installed in the case. No moisture on the wood, but you still got some benefit from having a wooden case, perhaps with a resonating chamber.
Regards,
Lowboy