Because this kind of reply gets posted every single time sleep deprivation is brought up.

Needing this little sleep is usually a lie or a self-delusion. Perpetuating it has negative consequences for the rest of us. Do some of these unicorns exist? Sure. But they are nowhere near as common as this type of comment suggests. Most of the people in question would be better off with more sleep.

Can they survive on 5 hours? Sure. Most of us can also survive on nothing but pizza. Doing this doesn't make you different, just unhealthy.