A pseudogene is generally not functional, since it lacks the promoter at the beginning, or since it is inserted in a region of the genome which is not transcribed. This is still "useful" in evolutionary terms, since it might be reactivated after some mutations occur. This (both with and without reactivation) is the evolutionary cause of homologous genes.

Some pseudogenes are, however, completely "useless" in this sense -- see processed pseudogene.