Your website doesn't clock off at five. So it shouldn't go down at five either.
When an online shop goes down, nobody rings to tell you. The orders just stop. You find out later, staring at a quiet sales report and wondering what happened. A slow site does the same thing, just quieter. People leave before the page has even loaded.
We watch the things you can't see, so the till keeps ringing while you get on with the rest of the business.
Offline means no sales. Keeping you online is the whole job.