Its important to serve pages of your blog in the shortest possible time. WordPress does lots of database queries to serve a page every time a page is requested. If your blog is a very simple one and you have enough resources, then you do not need to worry much. But in case you have heavy traffic and you are in short of resources, then you should go a cache plugin which serves static html pagesWP Super cache is one of the best cache plugin which I use.
If you have a site with considerable traffic and in short of resources like if you are using a shared hosting, then its adviced to use some plugin which serves static html files or in short cache plug