Sorry if there is answer for that kind of question somewhere, can't find it anywhere.

Take a look at obvious toaster example: If you live in Europe and have non-polarized plug and a toaster(bad one without double-pole turn off) - you have 50% chance of touching hot wire(via heating elements or even bread if you unlucky) if you will plug it the wrong way, so that the off switch turns off just the neutral wire. You will be shocked if you somehow connect your body to ground(through other device for example)

I understand that these conditions are not very likely to happen, but why many countries still not even thinking about throw away non-polarized sockets and have polarized? I'm sure even in Europe the light-bulb sockets are wired to be neutral-shell polarized, so why not wall sockets?

Sure it is not cheap thing to do, but 10 years later it will be even more expensive since more stuff will be produced without polarized plug.