First let me explain what I mean. 

This is an on-off switch: 

If you press the top part, whatever it's connected to turns on. 

If you press the bottom part, it turns off. 

On, off, on, off, etc etc. 

If you forget which part does what, they are conveniently labeled to remind you of their function. 

Anyway, looking around my desk I see lots of things that have switches that work exactly this way. 1. Printer. 2. Lamp. 3. Power strips.  

But lots of things don't. 1. Scanner. 2. Router. 3. Modem. 4. iMac. 

I seem to remember that my first Apple II had a simple on-off switch. Did the IBM PC? Not sure. The Apple III? Not sure. Pretty sure the first Mac did not have an on-off switch.  

Let's compare notes. Does your computer give you a clear and simple way to turn it off? If not, should it?