horribly low earnings :(

Can you please explain how not showing AdSense ads in off topic areas can increase what you are paid per click in on topic areas? I don't doubt you- I would just like to understand. I had assumed that ads in off topic areas would be contextually matched to whatever people are discussing in that area and it wouldn't matter that it deviated from the main focus of the site...

The problem is the relevancy of the advertisements. If you are showing the advertisements in off-topic areas then it can happen that you lose relevancy of your advertisements. When people are in your off-topic area and open your content area then in some cases they still see the off-topic ads.

The problem is that people then clicking the ads in most cases generate false clicks. False clicks because those people do not tend to buy anything on the advertiser's web page. If your website is about cars and then your advertisements are about dogs (assuming you have a dog sub-forum) then people navigating into the car area will most likely not purchase something after clicking the advertisement about dogs in the car area.

General Websites give you general ads.