Sometimes management says one thing ("This is really important!") but sends the opposite signal with their actions. Companies spend money on what they actually think is important. For example, my wife worked for a famous financial company that would sometimes ask full time employees to work on weekends - but never the contractors (they won't work for free). This sends the message that the deadline really isn't that important.
A friend works for a major defense contractor. They recently stopped paying for the first 5 hours of overtime. Managers still want their deadlines met so they can get their bonuses. Unsurprisingly, "You guys need to work for free so I can get my bonus" isn't a compelling reason for the employees (who don't have the same upside) to work longer hours.