For the same reason as disabling the Drupal core statistics module, one can disable the database logging module. It also fire MySQL queries on each page load. For truly optimal performance, for example on shared hosting or on hig traffic sites, you should definitely turn it off. This means you will have to use the server's error logs system. An alternative module is the Drupal core syslog module, which lets you log Drupal message to the Apache logs.
- Further reduce MySQL requests per page