Recently I asked this question:
It was pointed out in the comments that:
This is more of a "Yes, that's the way it works" than a "Why" issue. If you understood what a projection is, then the answer would be obvious. Unfortunately, GIS SE is an "on-point answer" place, so demanding an "elaborate" answer, when a textbook covers the topic in a chapter or three, makes this too broad for our Focused question/Best answer model.
Would modifying the question so that it asks about textbooks explaining this make it on-topic?