Because it's not simple. There are interests to be balanced and you can bet that defense counsel will challenge that decision pre-trial, at trial, and at appeal - and rightly so, it's not something that should be used with impunity.
Although creative writers love to put law enforcement characters on the horns of dilemmas like this because it makes for great drama, in real life the PIE does not get invoked that often because law enforcement doesn't want to risk blowing a case on it. Here, we're not balancing the public interest against all the rights of the suspect, but against his right to given notice of his legal situation. He could still clam up, ask for a lawyer, have one provided for him if he can't hire one etc., but the difference is that they're entitled under the PIE to ask him for information about outstanding risk factors (and only that) instead of giving him an advisory.
I'm guessing a bit here, but I have a hunch that if he said 'look, I set off those bombs on Monday, I feel terrible...' the interrogating officer would actually respond by saying 'we can discuss that later, now I just want to know about whether there are other bombs or weapons,' both because that's the actual priority and to avoid later legal challenges to do with 'fruits of the poisonous tree,' a colloquial term for improperly acquired evidence.
That's why I dislike statements like "party1's rights trump party2's rights." In reality, it's a balance, and that probably means that reasonable people can disagree on where exactly the balance point should be placed.
Although creative writers love to put law enforcement characters on the horns of dilemmas like this because it makes for great drama, in real life the PIE does not get invoked that often because law enforcement doesn't want to risk blowing a case on it. Here, we're not balancing the public interest against all the rights of the suspect, but against his right to given notice of his legal situation. He could still clam up, ask for a lawyer, have one provided for him if he can't hire one etc., but the difference is that they're entitled under the PIE to ask him for information about outstanding risk factors (and only that) instead of giving him an advisory.
I'm guessing a bit here, but I have a hunch that if he said 'look, I set off those bombs on Monday, I feel terrible...' the interrogating officer would actually respond by saying 'we can discuss that later, now I just want to know about whether there are other bombs or weapons,' both because that's the actual priority and to avoid later legal challenges to do with 'fruits of the poisonous tree,' a colloquial term for improperly acquired evidence.