[perlgeek]

Sure, our CI tool can run the unit tests from all the branches, but we don't have an environment for every branch where we can roll out the software, and do manual tests and automated acceptance/integration/smoke tests.

So if you have just one environment for testing, you can decide to deploy the develop branch to it, in which case you deploy untested builds (from the master branch) to production.

Or you can decide to always deploy the master branch to the testing environment, in which case you have to do a release each time you want to show somebody your progress (and you can't easily show it in dev); that's just annoying extra work, and goes against the idea of continuous integration.