Save or Die has a few sides to it (like most stuff found in D&D, usually)
It's a tool for the DM. There's a good handful of creatures in myths and legends that are said to "kill with a glance". Not "sicken and weaken" but "kill". Save or Die effects like the Bodak's gaze or a Banshee's Wail are simply the representation of that. The fact that player characters get a saving throw is the "hero bonus" that puts them above normal folks who simply die on the spot when encountering something like that.
It's a thrill. The thrill that life hangs in the balance of a die roll. It's the thrill of a gambler who bets all the evening's winnings on one lucky dice roll. The thrill of the player who had his fighter take blind fighting, of the group who has collected the rumors and KNOW something like a bodak is down there, but they go none the less, of the cleric who prepared the correct spells and can shine in one of the very basic clerical things...dealing with nasty undead, and triumphing through the graces of his deity over the forces of unholy undeath.
It's a Signifier of special power. There are not THAT many spells that go for Save or Die, and not THAT many monsters with it, either. Every time, it marks the caster/monster as something special, somebody to be reckoned with and not to take lightly. Sure, that's something that can be attained differently, too, but nothing makes people stand up and take notice than somebody who can point at a human being and make it die on the spot.
And as I already tried to point out in my last post, the Bodak is one of those monsters that had a specific use written in its background the first time it was published, a use that had the monster's special ability in mind. That background was dumped while the rest was kept, so all of a sudden a monster with a specific use became a generic monster to be judged fit as an encounter only by a CR number...I hope nobody will be offended if I say that it had to go wrong for many groups. And I also hope that nobody will argue that special monsters have no place in D&D, and that everything should be equally fit to be a random encounter in any old dungeon (although I remember similar remarks from discussions about Rakshasas and Ogre Magi

). Some monster abilities are for special-use monsters, not for random encounters, and should be used as such...and that assumption should be mentioned in the monster description. The MM series is not a collection of random encounters and cannon fodder, it is (or at least used to be) an adaption of legendary, unique and awe-inspiring monsters to AD&D as well as run-of-the-mill cannon fodder like goblins or orcs, and it would be nice if that would be again the case with 4E...3E is lacking in that respect in its first MMs.