Niche is also important if you are targeting for adsense but useful and good content also plays in order to garb the attention of your visitors that might force them to stay for awhile on your site. A visitors that will stay longer on your site will have also a chance to click on your ads.
It's true you can't write a few blogs and expect people to click on the ads you placed in them. There are subjects however, that seem to attract more clicks. But in general if you experimented with ad placement, your content is filled with the right kind of keywords to attract the right kinds of ads then you will get people clicking on your AdSense ads. If you want to get more clicks you need to experiment more with the placement of the ads in your site and possibly fine-tune the keywords in your blog. Good luck with everything and I hope you get more clicks in the future.