* Historical reasons: English spelling reflects a long history of language evolution and influences from other languages. The words "cable" and "label" have different origins and have undergone different spelling changes over time.
* Sound changes: The sounds represented by the letters "a" and "e" have shifted over time. In "cable," the "a" represents a different sound than the "a" in "label," even though both words are spelled with an "a."
* Borrowed words: "Cable" comes from Latin, while "label" has roots in Middle English. These language influences have impacted how the words are spelled.
* No perfect system: English spelling is not a perfectly phonetic system, meaning there's not always a one-to-one correspondence between letters and sounds.
In short, there's no single simple reason. The spelling of words in English is a complex mix of historical, phonetic, and borrowing factors.