Here's why:
* Quipu: The Inca used a system of knotted strings called *quipu* to record information. These knots, their position, and their colors conveyed numerical and potentially other types of data. Quipu was a complex system, but it wasn't based on letters or symbols representing sounds.
* Spoken Language: The Inca spoke Quechua, a language with its own complex grammar and sounds. However, they did not have a written form of Quechua using letters.
* No Need for Written Language: The Inca society was largely oral and relied on memory and storytelling for knowledge transmission. Additionally, their vast empire was governed by a system of roads and couriers, facilitating rapid communication.
While the lack of an alphabet might seem limiting, the Inca's system of *quipu* allowed them to efficiently manage their complex society and record important information.