Because new batteries have such high power density and the chemistry is fairly complex it's important that protection is built-in during charge, discharge and storage - otherwise pack life is shortened or damage can occur.
The smart functions control charging and protection so I'm led to believe - to prevent scenarios where batteries explode when charged or abused. Also to provide smart capacity indicators of course.
Maybe a gouge but didn't we have scenarios where faulty notebook packs were exploding a while back because some designer/manufacturer got it wrong?
