I think it's because it's an emotional thing, instead of a logical thing. If you were to look at it logically:
1. If you are religious & believe that God created the world & mankind,
2. Then shouldn't all parts of this rock floating in space be
equally important, because they were all hand-crafted during the creation process, and
3. Shouldn't humans be the
epitome of creation, therefore you shouldn't go around killing each other,
4. Especially just because you think one rock is more important than another rock (even though they had the same Creator!), and also
5. If you are all brothers & sisters spiritually, then what are you doing killing each other, especially because
6. There are 100 billion planets in the Milky Way (according to Mr. Google) & you're especially concerned about one specific patch of land?
Plus, if you're supposed to "turn the other cheek", then why wouldn't you just give the
other group control of said rock, because while it may be considered
more holy than other rocks ("rocks" being locations, buildings, artifacts, etc.), technically the
entire planet should be considered holy, as it was a spiritual creation, and even moreso, if it was created for the purpose of putting mankind on it, then mankind & our human bodies should be valued above all else, so you shouldn't go around killing each other in droves for thousands of years because now you're defeating the entire value system? But, we're emotional creatures, so, yeah

Meanwhile in the Middle East: