That is very naive. You can say that only because real and well organized attacks are very very rare.
Power Grid on its own is very complex system, and it is not trivial to revive it after blackout.
And second paragraph does not save it. Weak spots are everywhere. A few guys with rented trucks could cause blackout in several counties for weeks.
and yet, we do it on the regular.
edit:
> real and well organized attacks are very very rare
and why is that? if the system is as vulnerable as they say and the world is as full of enemies as they say then why is it not constantly going down?
No, we don't. When the whole grid is down the power stations have to shut down - they can't run without load. Power stations require power to start up, and without power on the lines there's no synchronisation.
There are facilities designed to start a grid, the utilities are prepared, but it generally takes 6-8 hours to get synchronisation to a level where the main generators can get back online.
As most major generators are a long way from population centres (and their primary load) a coordinated attack could partition most country's grids in a way that ensures a long term blackout.