Importance of PortalSiteMapProvider in WCM?

PortalSiteMapProvider provides a nice automatic caching infrastructure for retrieving list data. The class includes a method called GetCachedListItemsByQuery that was used in this test. This method first retrieves data from a list based on an SPQuery object that is provided as a parameter to the method call. The method then looks in its cache to see if the items already exist. If they do, the method returns the cached results, and if not, it queries the list, stores the results in cache and returns them from the method call.
SPQuery strQuery = new SPQuery();
strQuery.RowLimit = 1;
//Retrieve the items for the specified Target location from the Target list
strQuery.Query = "CAML query...";
PortalSiteMapProvider ps = PortalSiteMapProvider.WebSiteMapProvider;
PortalWebSiteMapNode pNode = ps.FindSiteMapNode(web.ServerRelativeUrl) as PortalWebSiteMapNode;
SiteMapNodeCollection pItems = new SiteMapNodeCollection();
pItems = ps.GetCachedListItemsByQuery(pNode, "targetListName", strQuery, web);
//Check if there are items for the specified target location
if (pItems.Count != 0)
{
try
{
//Retrieve the most recently created item for the specified Target location from the list
foreach (PortalListItemSiteMapNode pItem in pItems)
{//TODO}
catch (Exception ex)
{}
}