Ask HN: Why don't companies hire programmers for fewer hours per day?
Salary is only roughly half the cost of employing someone, so while a 25% salary reduction for 25% fewer hours is fair for you, the employer is not seeing a 25% cost reduction. They're not saving 25% on payroll taxes, benefits, workers comp, PTO, training time and management overhead. In fact, more people working fewer hours increases most of these costs.