Final answer:
The passage does not mention Billy or an EPIRB, instead it describes a character signaling for help by waving his coat. A lack of context prevents a definitive answer to the question of why an EPIRB isn't activated.
Step-by-step explanation:
The extract provided does not mention an EPIRB (Emergency Position Indicating Radio Beacon), which is a device used in maritime distress situations to alert search and rescue services. Instead, the character referred to as 'he' appears to be signaling for help by waving his coat. The text suggests a lack of understanding or desperation on the part of the observer, who questions why more proactive measures, such as sending a boat, are not taken. The conversation implies that they expect the individual in distress to take action, such as activating an EPIRB, assuming one is available, but the text does not explain why this hasn't happened. Without more context or details about the situation, including whether an EPIRB is even available to Billy, it is difficult to provide a definitive answer to why doesn't Billy switch his EPIRB into on?.