When To Work

When it comes to your job, it mostly makes sense to let your employer (boss, manager, or whoever is in charge of your department) direct what work gets done, who gets it done, and generally how it gets done. What I never understood was why it ever mattered to my boss when the work got done. As long as my portion of the deliverable was submitted by (or before) the deadline: why would anyone care when I did the work?