Com_commit and Com_rollback count are almost same. What doest it mean?

SHOW GLOBAL STATUS has Com_* variables: The Com_xxx statement counter variables indicate the number of times each xxx statement has been executed. When I compare Com_commit to Com_rollback, both are almost equal. I do not understand how is that possible. My understanding is that you commit transactions and any rollback is done only when required. Then, why these values are so close? We have only one database that is used for application (Jira) and it uses READ-COMMITTED Transaction Isolation. There are no other procedures in the entire mysql that does any operations.