... my preference is to keep it running. It isn't just the time to boot, it also is the time to open all the windows I work with (my task bar shows me upwards of two dozen entries at an one time.) to get back there after a reboot takes between 30 and 60 minutes, and I am not keen to go through that too often.
Now in my part of the world the monopoly electricity provider has neglected the power grid to the extent that they run out of capacity from time to time. Their way to resolve that is to shut down the consumers, one suburb at a time, for four hours.
So, if your livelihood depends on being able to compute you have a setup with large batteries and inverters that make mains power (or a reasonable lookalike) out of the power in the batteries. Once power is restored your batteries will be recharged.
If, like me, you run, say, a half dozen PCs you probably don't have enough battery power to run them all, including peripherals etc. for the four hours (plus safety margin.) So, not to lose your place, you put computers to sleep (rather than switching them off) before you retire. The idea is that you can run two computers for the four hours and there is enough power left to support the sleep mode of the other four.
That's what I use sleep mode for.
Of course, it doesn't help at all if one of your computers wakes up and sits around using up a full load all by itself, only to drain its battery, so that it and any other machine on the same battery will unceremoniously come to a full stop, flying in the face of Windows's desire to be shut down properly or - in the event of an update - break that update in the process. You have seen the message "Do not power down your machine. There is an important update running." When this happened to me once in the middle of a seminar I was running I let the audience take a vote if this meant that I had to throw the computer out the window using an extension chord ...
Ironically, it was the dreaded Windows 10 updates that woke up my machines at night. There is a setting somewhere that allows or disallows waking up a computer for "important" updates. When I discovered that I dug around and found that setting and turned it off. Now I can't recall where that was ...
The obvious other possibilities are LAN, mouse or keyboard. Mouse and keyboard are a must if you live close to the San Andreas fault or any other source of movement in your building structure (mines, volcanoes, train tracks or airports, etc.) LAN is a good idea even if there shouldn't be anything on your network.
So, to finish my story above: The computer that wanted to do an update woke up, started draining the battery, found that my network settings didn't allow it to download the update anyway, and stayed awake, stealing the energy from the other machines that were trying to do useful work - and thus the lot of them came down when the power ran out.
(Maybe I should also unplug the network cable when I put a machine to sleep ...)