In terms of in-office hours, that's not really true; it's more of a programmer thing. It's pretty common for engineers in other fields work regular 40-hour week

In terms of in-office hours, that's not really true; it's more of a programmer thing. It's pretty common for engineers in other fields work regular 40-hour weeks, unless something unusual is happening. Partly this is because the classic professional workplace has fixed hours: 9-5 or 8-4. Many people have no choice but to stick to those hours closely, because they commute in carpools, so you can't go in early or stay late unless you convince the whole carpool to do so. Admittedly, it is getting more common to do some email in the evenings nowadays, which sneaks in some extra non-office work hours.