Starting with CU3 and together with the Lync 2010 functionality enhancements for autodiscover and Lync mobility services coming with CU4 the update process included larger modifications of the Lync database schema. Since then the database update is listed as a necessary step in the release notes. This is for purpose because of smaller tweaks that come from time to time. It looks like there have also been some in the CU released in April 2014.
September 9, 2014