By increasing your CTR, working on the keywords in your content, increase the relevancy of the ads in your site. There's a lot more, just don't feel like typing all that. ;-)
my friend some pepole think what is meaning of CTR ,then know, if your website have unique content and your keywords unique when google ad will appear on your site to catch that any unique keyword,then CTR will be hight,if you keywords will be common then CTR will be low.
I thought you are gonna disclose any mystery when i read your title. Basically traffic is earning... no traffic no earning >> very simple
Dont be lazy and go get some traffic!!!! Its like saying: "I want to go from A to B in my car - but I dont want to put any gas in"!!!!