Some work doesn't happen any faster despite worker productivity. The 40 hour work week isn't determined by the output, but rather by the income the worker receives. People are free to work 15-18 hours a week, but they don't.
I'm forced to work 40 hours per week no matter what I'm getting paid or I get fired, not sure how this is a 'choice'.
Not if you live in the US and want health insurance.