What are the advantages and disadvantages of cleanliness?

I don't see any advantages to uncleanliness.

Advantages include: Health reasons, odor, varmint infestation

There seems to be some research saying that in moderation some uncleanliness might a factor in better health, lowing the risk of Crohn's disease, allergies, auto-immune diseases and a growing handful of other disorders including depression.

( re-read the words up there-  in moderation )

You become like a skunk a no one wants you around

There is no disadvantage of cleanliness. But there are advantages of it like; pollution free environment, pest free area, good health, clean air. And many more.