[srer]

Software updates is one reason

For simpler userspace updates a restart of the relevant processes is easy enough, but it can be a bit more difficult when it comes to kernel updates.

(Updating a running kernel has been a thing in Linux for a number of years, but my systems don't do it.)

[taylodl]

Software updates require a restart, but that's not what I'm thinking of when I consider a power down. I'm thinking of the scenario where you take explicit action to power down your machine and leave it powered down. I power down my machines before going on vacation, for example.

Even when you power down or restart a Mac it remembers all the applications you had running and all the application windows and it re-opens everything so you come back to everything just the way you left it.