Having your keywords in the title lets Google know what the page is about so that it can place the site in the best location for the given subject. If you have a keyword in the title and the content of the site, it makes it easy for google to determine what the page is about.
You have to remember, Google is a computer and does not have the ability to reason, so you have to give it something to work with so that it can know what the page is about. And that is done with keywords in the title and content and many other ways also.
Spend some time reading and the
seo forum and you will soon put it together.