Judging by the comments from MacMan and David63 versus the other posters, I think that a distinct energy use culture is being displayed. In Europe, we generally switch stuff off when it will not be used shortly. Electricity is expensive in Europe, but there are still some people who haven't worked out why their bills are so expensive: just turn it off and save money.
The "wear and tear" argument is a bit of a myth. In "ye really old days of micro computing", switching off frequently was bad. But that hasn't been true for twenty years. There are exceptions, of course. A company for whom I worked ran a Corvus hard disk continuously, because it didn't like being turned off. But temperamental hardware like that is unusual and my old computers are much healthier because they don't whir, spin and generate heat unnecessarily.
At the same time, don't get over obsessed by energy saving. One of my religiously green colleagues goes around in the evening switching off TFT monitors that are in "power on, no signal mode". Over a couple of evenings, I measured how much energy this exercise saved: 0.01 KWh per night, cost saving £0.0006. My colleague's blog proclaims that if this delays a worker by two seconds when they start their computer in the morning, it is still a worthwhile saving. Wrong. Two seconds of my work time costs my employer orders of magnitude more than £0.0006.
And a further, at the same time... Modern Macs are very efficient in sleep mode, but it is not an excuse for leaving them on. Wake up time from sleep: 10 seconds. Startup time from cold: maximum 240 seconds. Sleep mode provides a 230 second difference in availability, but for all of the sleep time, you've been giving money to your electricity supplier. Pointlessly. If the loss of 230 seconds of home life is distressing, flip to YouTube on another computer and watch inane videos that defy Darwinism. Shutdown if the Mac will not be used for a while; use sleep when you expect to use it.
