The short
answer is:
1). Insect damage
2). Messy
3). Promotes rot
Most insect damage, not just termite damage as you might think, but all kinds of insects are attracted to wood that has decaying bark. There is a stage after the tree is cut, and before the bark falls off on its own, that insects are attracted greatly to the wood. By removing the bark first, you mitigate the effects of insect damage to the wood.
At the same time, as mentioned before, as the wood dries the bark inevitably falls off. Not always in sheets and at the same time, so it ends up being really messy. Since this is about a year later, it coincides with when the house is being outfitted inside and really can make a mess. It is not the end of the world if you don't mind cleaning up lots of mess now and then, but debarking first can avoid a lot of mess.
As we all know bark on a tree protects the
trees, but after felling that bark also expedites rot. Since the tree is no longer growing, but the bark still ensures the tree stays wet, it can promote rot. This is why an unbarked
fence post rots faster then a peeled one.
I had the same thoughts as you at first, and wondered if spending the time to peel the bark off a log was worth it. Now I am trying to come up with a debarking method that is easy to cobble up in do-it-yourself style instead. Kind of going with the thought that spending time up front to come up with a mechanical debarker would be a better method then spending countless hours debarking by hand. In this regard YouTube has various videos on how to accomplish this. I have not seen any I like, but have noticed my bulldozer tracks debark quite easily in the right circumstance so I am curious if I can build something that will enable my bulldozer to do the debarking for me.
At the same time, if you find you must hand debark, doing so now until June is the best time as when the sap is running, the bark peels much easier. You will also want a Spud, a long handled tool for peeling bark.