Why did it take so long for blogging to take off?

From Paul Graham’s “Hiring is Obsolete” (May 2005):

Have you ever noticed that when animals are let out of cages, they don’t always realize at first that the door’s open? Often they have to be poked with a stick to get them out. Something similar happened with blogs. People could have been publishing online in 1995, and yet blogging has only really taken off in the last couple years. In 1995 we thought only professional writers were entitled to publish their ideas, and that anyone else who did was a crank. Now publishing online is becoming so popular that everyone wants to do it, even print journalists. But blogging has not taken off recently because of any technical innovation; it just took eight years for everyone to realize the cage was open.