As admin, you can set whether the default front page is the Site home or the Dashboard by going to Site adminstration and then Appearance and Navigation - the default is Dashboard but you can change it to Site home. See also Dashboard and the section on default home page.
I think it is quite useful, once a user is enrolled in some courses, to see them and their progress on the dashboard and therefore have the dashboard as default. You can add an HTML block to the default dashboard with a note and a link to Site home if you wanted to, thereby keeping the dashboard as default and pointing them in the direction of Site home. See HTML block