There are a lot of things that need to be done to put together a complete site. Site management can encompass a lot of things from blog entry to website updates. The latter, is why I usually want to get a maintenance agreement. With the web still like the wild west, and the inevitability of all code being vulnerable, we need to keep systems as up to date as possible. This in turn, reduces down-time, and keeps your site ready to inform, or enrich the people loyal to you or your brand.