Why is Z so rare?

Why is the letter Z so uncommon?

In 300 BC, the Roman censor Appius Claudius Caecus decided to eliminate the letter Z from the Roman alphabet, supposedly because he found it unappealing, stating it resembled a corpse's tongue. However, a more plausible reason is that the sound associated with the letter had faded from the Latin language, rendering it unnecessary for the spelling of Latin words.