Sleep mode?

Why does every thing have a "sleep" mode?  Lets be honest it's not really saving any power, my monitor doesn't exactly need a new power station online every time I turn it on, same with most TVs. 
Trouble is it's a royal pain in the arse to have to keep pressing a key to keep the bastard on, it'll even shut itself off when I'm copying a memory card onto the PC.  Now I know I don't really need the monitor on for that job, it'll do it on it's own, but I do like to see when it's finished.  So why does it need me to be dancing the Highland bloody fling on the keyboard to stay on?  My good old CRT monitor doesn't "pop off" for a kip every 45 seconds.