Once upon a time, I worked night shift hospital IT. The work had a lot of downsides (crap pay, crap hours, skeleton crew, knowledge-free users), but it had a few good points, too. The nature of the work meant that I had the keys to the kingdom, and the skeleton crew meant that more often than not, nobody would be looking for me, and if they did they had my pager number. (This wasn’t so long ago that pagers were still a thing in the general public, but in hospitals, pagers were still going strong as late as a few years ago. For reasons.)
The thing about hospitals is, there are a lot of areas that shut down after normal business hours. These areas often needed work done, and that work often got put off until night shift, because it’s easier to fix a PC when nobody’s working in the area than it is during the day, when some end user is probably actively trying to destroy it anyway. (I’m not bitter.)