Hi Joe,
I noticed this myself recently and have it fixed for the upcoming release. It can also be fixed immediately very easily. Using a text editor open the /Admin/PageSettings.aspx file and look for this:
<asp:CheckBox ID="chkIncludeInSiteMap" runat="server" CssClass="forminput"></asp:CheckBox>
and change it to this:
<asp:CheckBox ID="chkIncludeInSiteMap" runat="server" CssClass="forminput" Checked="true"></asp:CheckBox>
Best,
Joe