Colorado would like a word.

I’m mostly kidding, but not entirely. The point is that they work (only?) when there are no cultural/religious/tribal implications and are merely for administrative purposes. It’s really the reason why the borders on the east coast of the USA are so messy compared to those past the Mississippi.

I suspect that native Americans would like a word with your word.

That's hardly a Colorado-specific issue. They were wronged from day 0, and forcibly evicted from their ancestral lands.

Exactly my point.

Probably only in Antarctica. But that is not because the lines are straight.

I don't think it is really about straight lines, most borders are probably where they are due to some circumstances involving lots of violence. It's just that straight lines are a modern concept, so the related violence is more present in our minds.

Geographical features, such as mountains and rivers, don't form straight lines on the map.

Yea, but just as an example, determining that the Rhine forms the border between Germany and France probably goes back to Roman times, and probably also involved a lot of genocide.