I just saw a YouTube video of a landing airliner with the gear not fully extended and the cabin crew gave the instructions "Stay down! Heads down!" repeatedly to passengers but without any technical help like PA. Why is that the case? Why don't they use the PA system for commands like that?
Not knowing that specific video, impossible to tell the scenario.
But in general, you want to not have to rely on technology in an emergency situation. What if you were trained to use the PA system but there is no electricity? So you train to shout and use non-verbal communications to get your point across in an emergency.
She is strapped in and won't be holding the PA handset in the final moments because it can be a dangerous missile in a crash.
And they can get by without it. Most of an FA's training is in how to speak, project and dominate in chaotic situations. They are effectively riot cops you might say, with extensive training on crowd/person control, who are likely to spend their entire careers working undercover as waiters/stewards until that one in a million moment comes along like in that video.