I tend to leave my computer on for random reasons. Specially the ones that the motherboards lack a means of sleep mode. I dislike to be working on something long and lose my spot. Then have to scan tons of lines following the bread crumbs per se to get back to what I was working on. Not to mention uploading files during my downtime is a plus.
I hate to turn off my laptopt, it take minutes to start up, I always turn it in sleep mode and when I need it, I just press ON-OFF Button.
If I let it on overnight, probably I download large files from torrents.
I used to use Hibernate mode in Windows Vista, and 7, and it seems to make Vista-7 start up a lot faster.
But, since I now use Windows 8.1 which boots up in 30-50 seconds even on a older 7200RPM 320GB mechanical hard drive, I just shutdown my computer instead of hibernating it.
I also own a Google Chromebook with a 16GB SSD drive, and it starts up in under 8 seconds, so I just shut it down to save battery life, and rarely use sleepmode since the bootup times are so fast.