NPIP is usually not something for backyard flocks since it was designed to protect the food supply, not to certify flocks disease free (which it does not do). If you show or you are a breeder, it makes sense, of course. If you intended to mail out hatching eggs as a breeder or start sending live birds through the mail, you would need that.
If it included mycoplasma testing, it would make more sense for a backyard flock owner. In most states, maybe all, you can get that extra test for extra $$$, but it must be done quarterly, if I recall, not annually like the P/T.