A shutdown and a fresh start also deletes files that aren't used anymore and the PC does check itself for hardware problems. Starting a PC could take a long time in the past, but my current 7 year old system starts in about 10 seconds, a newer system could start faster. I also turn off all peripherals like monitors and printer etc. with one switch after the computer is off, to make sure there is not a single light still wasting electricity. Standby devices in a common houshold use so much electricity, that it amounts to a lot of money over a year. But I guess we are still in the phase of convinience over climate and people have money to waste too.