The CRM 2011 ribbon had many commands as part of the Out of the box ribbon and most customers had to edit the ribbon to remove a bunch of commands to make it work for their system. Our user feedback suggested that the ribbon felt mostly crowded and the participants in our user studies identified the core commands that they use as part of their daily job.
As part of the design to simplify the number of commands that appear and surface the most useful commands, Microsoft Dynamics CRM 2013 does not display some buttons that appeared in prior releases. For example: The Mail Merge and Run Report buttons do not appear for all entities. These buttons still exist in the underlying XML definition but they are hidden from appearing in the user interface. It is possible to restore hidden buttons using the XML definitions documented in the Microsoft Dynamics CRM SDK or as mentioned in the following blog post you can use 3rd party tools such as the Ribbon Workbench to simplify the process.
How to restore a hidden button on the CRM 2013 Command Bar
Thanks,Anusha Shankar & Dana Martens