I remember an occasion when I lived with a partner - the fire alarm had gone off and I immediately got out of bed and started putting my pants and shoes on. She asked why, I said "so we can go outside. What are you doing? Let's go."
She said she didn't understand the point - if it was a REAL fire, wouldn't they just come get us or tell us?
I don't know how prominent this thought process is, or why so many people don't take things like fire alarms seriously. Selection bias, perhaps you're right. Every fire alarm most people has ever heard was a drill.
This has happened twice at work now, even my manager was teasing me for telling people they should leave. Eventually I left on my own.