The Mystery of the Missing N

I'm pondering the mystery of the missing N.
Well, it's not utterly missing, but certainly obvious in its lack of prevalence.
Of 169 surnames in a book series, some letters never appear at the start of any of the surnames.
Those MIA are, as one might expect, UXYZ and... N. Even I and Q score 2 names each!

The plot thickens.

In case you're interested (you're probably not) here are the surname-initial scores.

N U X Y Z  - zero entries each

I J Q V - two entries each

K W - three entries each

E R - four entries each

O - five entries

G - six entries

P - nine entries

M - ten entries

L T - eleven entries each

F H S - thirteen entries each

A - fourteen entries

B - fifteen entries

D - eighteen entries

C - nineteen entries

That did surprise me. The C-folk are called...

Caffrey, Canterbury, Carpenter, Cassidy, Chalk, Chance, Chancery, Charming, 

Cliff, Clover, Cobbler, Comice, Connemara, Corneau, Cornfellow, Cottman,   Cowrie, Creed, Curry

Note to self - investigate surnames beginning with N...