Solitary letters

I , J , K , are solitary letters. In any kind of reference work they are among the few letters that have the least entries. For example. A movie guide is often alphabetical, but I find that the movie titles under the letters I , J , and K are few. For a language or English scholar this may be a reason to ask, why? Yet for anyone who is interested in the English language and the construction of words a reason to find out more. Why are I , J , and K among the most solitary letters? And when these letters contribute to words, they make for the most lonely of words.