This is a feature I've been wanting to have for quite a while as well.
I run a few different printers as part of my job and demand for them can vary, but in case of urgent requests I tend to keep longer prints for overnight. For example, I have two 17 hour prints I need to set to go, I want them to start as late as possible in the day to keep the printers free for as long as possible during work hours, while also still having them finish before I come in tomorrow.
At the moment I just try to remember to set the prints to go at the right time, but because running the printers is just one part of my job, I'm not always going to be free at the time the prints need to be started. Being able to schedule them to start at a specific time will make things much more flexible for me, I could prepare a print in the morning and not have to worry about it, while still being able to set prints throughout the day.