Well, I've seen lots of studies over the years that claim that extra time spent in the office (beyond 40 hours per week) doesn't translate into extra productivity. Some reasons mentioned include:

- Tired employees make more errors, which then take time to fix. And if you've been working for 12 hours, you'll be mentally tired even if you're not physically tired.

- If you spend 12 hours a day at the office, lots of things you need to do in your life (e.g., arranging your social life, running errands, going to the gym, eating meals) will get done while you're at the office.

- A lot of programmers (myself included) get their best thinking done when they're relaxing away from the office.

Maybe not extra actual productivity, but extra imagined productivity and when it comes time to raises, it's not reality, or what could have been, but your boss's imagination that counts.

I don't think bosses who want long hours are all that interested in actual productivity (which, especially with software, they don't seem all that capable of measuring anyway). I think they simply see it as a signal of loyalty.

I think you (and I have noticed it elsewhere here) have nailed the main cause for the discrimination based on gender (and probably also age) that is really counter productive for the society as a whole.