I have never understood that as an answer when attempting to find better ways to do things. I hope I never do understand it. While there’s something to be said for the axiom “If it ain't broke, don’t fix it”, I have always considered a person who resorts to the argument “because we've always done it that way” to be closed-minded, obstinate, and inflexible. It is nothing less than inexcusable to me when this is used as the first line of defense and the person using it expects this to end all discussion on the matter.
I offer up the following as an example to demonstrate why I feel this way.