We question this too, at first.  However, there is a pretty good reason for it. Below is the explanation provided by State and Board of Election resources.

​

NC state law, and the Union County Board of Elections, require that each person who signs a referendum petition, provides their birthdate, so they can verify that each signature, originates from:

​

(a) a unique individual, 
(b) who is also registered to vote, and
(c) who is also eligible to vote in that city's municipal elections  

(ex: the registered voter lives in Marvin's jurisdiction)

Since there are often several registered voters, with the same name (and sometimes the same name and address) living in the same city, the birthdate ensures officials have validated the signature against the right voter information.

 

​