If you have multiple branches open, and have to switch between them, it is often nice to leave your branches fully extended so that you can access all branches without navigating in or out through the drill downs... This feature is not consistent.
I regularly navigate to any other program, only to come back to SourceTree within the hour and have all of my drill downs closed. This does not cause a loss of work, or does not damage anything, but is a nuisance.
Correction: The amount of time it took to write up this JIRA item was enough time for SourceTree to decide to do things on it's own, didn't even have to close the application. The application should not do anything without the user expressly telling it to do so.