Without having looked into it, my impression is that the popularity of astrology (and psychics, etc.) is down to the fact that they tend to make broad, vague predictions with a relatively high P(E) that people (emotionally) tend to underestimate. For instance "something bad will happen to you this month" -> "OMG, I stubbed my toe the other day, they were totally right". If we're accurate at assigning P(E), however, then we'll probably end up with a low P(H|E).

The prior P(H) is also arguably trouble. What's a good prior likelihood for the hypothesis that magic sky gods affect your fortune? I don't know, but I'd probably have to start somewhere pretty low.