Here's why:

* Hox genes are a type of homeobox gene. Homeobox genes are a family of genes that play a crucial role in the development of body plans in animals.

* Bacteria are prokaryotes, while animals are eukaryotes. Prokaryotes have a simpler cellular structure and lack the complex developmental processes that eukaryotes have.

* Hox genes are involved in the complex regulation of developmental pathways. These pathways are not present in bacteria, which have much simpler developmental mechanisms.

In summary, Hox genes are specific to eukaryotes, particularly animals, and are not found in bacteria.