While there are a small percentage of people who genetically require less sleep, 4.5 hours day in-day out would result in severe sleep deprivation symptoms in the vast majority of people. I know after a couple nights in a row with 6-7 hours of sleep I basically become pretty non-functional and I always get sick.
It's true.
I've met people who slept 3 hours a night regularly to make ends meet. They seem and act normal until you try to have a conversation with them or ask them to do something outside their routine or that requires thought.
You'd be surprised how much of human social and work behavior comes automatically. You can sleepwalk through modern life and never have to wake up.
They were even capable of getting passing grades in university. Even some kinds of learning come mechanically.
Any less sleep will means my productivity drop off rapidly and makes error and judgement that I need days to recover from.
Another reason why I believe there should be some government regulation, or little regulation but worker union.
Unsurprisingly there is such regulation in Europe. It's illegal to work over certain amount of time -- it's the employer that potentially gets into trouble so this is usually observed as far as I know. There are allowances for short periods of overtime, but strict limits over longer intervals.
"Death march" as commonly used in English-speaking nations is typically used as hyperbole or dark humour, whereas in Japan "karoshi" is used in a clinical sense for documented cause of death.