Because it is a matter of original message. The Ethereum devs have had one mantra from the start: code is law. What is written in the code is what the developer means. There's no room for interpretation.
But, somehow, when someone did something allowed by the code, it turns out it wasn't in the spirit of the law, and so should be forked.
> The Ethereum devs have had one mantra from the start: code is law.
Oh great, now I can actually say something to my ethereum loving brother in law, btw do you have a source for this? Because when I try to search for any resource on the internet from before 2016 where Ethereum developers said that "code is law" I can't find it.
But, somehow, when someone did something allowed by the code, it turns out it wasn't in the spirit of the law, and so should be forked.