I think WMS7’s experience working overtime to complete a project on time is likely a main reason people work overtime. while many people are motivated, the motivation is not necessarily to finish the project early but to finish the project in general. poor performance at work will eventually lead to being fired. That being said, overworked and sleep deprived employees ultimately harm the company in the long term as productivity inevitably decreases.

https://hbr.org/2006/10/sleep-deficit-the-performance-killer
https://hbr.org/2015/08/the-research-is-clear-long-hours-backfire-for-people-and-for-companies