I'd agree that in a perfect scenario, you should be able to push code at any time confidently. But for many companies and projects this is not really available.

I'd agree that in a perfect scenario, you should be able to push code at any time confidently. But for many companies and projects this is not really available. As well, in many organizations the person who has to fix broken stuff is not the same as who develops and pushes code. I'm not saying that's a good thing, but it is reality for many people. Even if it only happens once in your career, once you've had a dev push out code at 5pm friday night, jet out the door and hit the bar, meanwhile you (the sysadmin/ops on call) get woken up at 1am by site down alert, and have to debug/rollback the changes while the dev who pushed them is unreachable, you learn to really avoid friday evening pushes. Fool me once...