The disadvantages of using Google AdSense:

• The disadvantage of Google's AdSense Pay Per Click service is that you only get a small part of the cash from each click. It's only a few cents on the dollar.
• They don't say what percentage of the click income went to you. If I had to guess, I would say it's around 5% or less.
• They also don't inform you which advertiser Ads are being clicked on, making it difficult to decide where to concentrate your content in order to generate more money.
• One of the most significant drawbacks of AdSense is that it occasionally displays ads that are unrelated to the content of the site, which can detract from its overall appearance.
• The 'Ads by Google' credit given below each ad is free promotion for Google; if your visitors click on this link, you gain nothing.

Read More : What are the pros & cons of Adsense HeatMap (best Google Adsense placement tool)?