Why don't voice radio communications use FM?

Emily writes:

They were misunderstood a) because people were stepping on other people
and b) because the KLM crew had heavy Dutch accents.

The reasons why they were misunderstood have never been ascertained,
and there are several possibilities. It's not even clear how much was
understood or misunderstood, since a number of the people involved are
dead. The common point to all the possible scenarios is misunderstood
radio communication.

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