Suppose I have a grass hut. Suppose you also have a grass hut.

Now assume that they are both at risk of consumption by fire. Assume, further that each is at risk from the other. If my hut catches fire, it is at risk of spreading to your grass hut. Likewise, if your hut catches fire it is liable to spread to and consume mine as well.

Now, suppose you take a precaution -- you blaze a firebreak around your grass hut. Now, if my grass hut catches fire, yours is no longer in any danger, and if you grass hut catches fire, it will be sure not to spread to mine.

NOW.

Why would you possible want ME to build a firebreak too??!