At work, we always left them on because the LAN admins would push out software updates at night.
At home, I turn them off daily, not so much to save on electricity but because when the pc's on the fan basically acts as an air filtration device (collecting more dust inside the pc), and also to give the non-SSD hard drives and power supply a rest. All 3 components still have a mean time before failure.
Someone that's hyper security conscious could argue it's more secure to turn off a computer when it's not being used, rather than having it online 24x7.