Because I personally do no like having a function returning an unexpected result.
If a condition can be called only inside a certain trigger and it gets called outside said trigger, in a normal programming environment it should raise an exception.
Since as far as I know there is no exception handling in Construct, it would make sense to have a parameter in the condition that forces the user to place that condition only inside the specified trigger, if not it should display (in the editor) a warning or an error, sort-of like how the Local Storage displays the [Certain events can not be moved due to restrictions on the trigger].