I'm on the other side of the coin. I view the associated costs of working in an office as built into my salary. For example, if I go to an office, I suddenly now have to buy gas/repairs for my car, I have to buy office clothes, and I have suddenly lost days per year to commutes. If I work from home, I see myself as freed from those costs.

Put another way, I see my salary as the sum of the cost of the work that I do PLUS the costs associated with me getting the job done. Working from home is simply more economical (and my work/life balance is significantly improved).