Earn money from Google

Keywords and Labels are important as Quality and Unique content. A quality and unique content without keywords and Labels have less chance than the moderate content with proper keywords and labels.

Keyword for Search Engine:
Labels for blogs or keywords for website were the most important thing for any webmaster or blogmaster. These are the words which are given importance by the search engine. Any way the huge database of search engines has their index of everything, but the keywords and labels you give are given prime importance. In blogger the option for including labels is given in the post page. It is located in the lower right corner. Just give the keywords separated by commas.
Keyword for Adsense:
Labels and keywords were important for adsense and should not be ignored. Since keywords are the words that are used in searching the content. As per the keywords your pages will be categorized in their sections. So if you miss a keyword you will miss many of your potential visitors because of missing the keyword.
What happens if I miss the keywords/labels:
If you miss the keywords and labels there is a possibility of adsense showing a general ad on your page. If you display a general ad or irrelevant ad which your visitors are not interested in, you may miss a chance of a click from that visitor. Imagine you get thousands of visitors a day. How much earnings you will be loosing just for not using your keyword or label.