Here is a partial quote from a reply I wrote concerning building thatch roof as opposed to concrete.
Thatch may have a disadvantage at certain times of the year, usually in the wet season more so than the dry season. It can harbor insects and reptiles which like to nest in the thatch such as spiders, various small lizards, and others. It can be quite a surprise to be sharing a bed with a spider or worse.
Hope this helps to answer the "why nots?"