a traveler comes across a fence

Chesterton's fence:

A traveller comes across [a fence], thinks “I can’t think of any reason to have a fence out here, it sure was dumb to build one” and so takes it down. She is then gored by an angry bull who was being kept on the other side of the fence.

Chesterton’s point is that “I can’t think of any reason to have a fence out here” is the worst reason to remove a fence. Someone had a reason to put a fence up here, and if you can’t even imagine what it was, it probably means there’s something you’re missing about the situation and that you’re meddling in things you don’t understand. None of this precludes the traveller who knows that this was historically a cattle farming area but is now abandoned – ie the traveller who understands what’s going on – from taking down the fence.

- Slate Star Codex

This applies to any kind of change: you’ve got to understand why something exists before you remove it. I’ve definitely seen this with legacy code. There tends to be a reason why that weird bit of cruft is still around.