Why pretty blogs usually suck

This essay is good from a high level, but I don't think it really explains why pretty blogs usually suck.

The "pretty blog" effect goes beyond blogs. The same thing happens with video, audio, etc. There is a pretty strong inverse correlation between the amount of production value and the amount of actual value.

My hypothesis is that it's because of resource allocation -- the more resources spent on aesthetics, the fewer are being spent on the substance.