Exemple with the search engine :

the css <link href="{$contextPath}/plugins/web/resources/css/service/search.css" type="text/css" rel="stylesheet" />
is in the <xsl:template match="/search">, if I want not to include it I have to override all the <xsl:template match="/search">..

if there was a <xsl:call-template name="service-css"> like the <xsl:call-template name="extra-css"> it could be easier to override.