Thoughts That Go Bump in the Night explores concepts that are often novel, obvious, subtle, and sometimes mysterious. The whole arena of habituation is the basis for Habits, Patterns, and Thoughts That Go Bump in the Night. This video, highlighting an experiment in social conditioning, further demonstrates the subtle ways habituation can drive decisions and behavior. The old saw "we've always done it that way" had roots in something. The something may or may not have been valid, useful, meaningful, etc. But, there was a something that was established as a norm, and members of the community (be it tribe, party, faith, race, etc.) were trained to follow it.
The good news, of course, is that the process of habituation is continual and neutral, and with awareness, more effective and productive routines can be established. But, you get an idea how entrenched belief systems can be established.