By Default, SharePoint Allitem.aspx doesn't display attachment for the list items which have. So the question now is How to Display it?
It's pretty simple and straightforward. Just add the add the following code in allitems.aspx page through SharePoint designer. The Job is done.
<SharePoint:AttachmentsField runat="server" FieldName="Attachments" ControlMode="Display" Visible="true" ItemId="{$thisNode/@ID}" />