Expatriation means losing basically every right in the charter, and is politically equivalent to execution. This reason (failing to vote) is also heavily biased towards people with less control over their lives, and disrupting someone from voting could be used as a weapon.

I can see punishments for failing to vote, but such an extreme response should be reserved for those who explicitly choose not to vote, and such a system would need a rigorous judgment to act on.

Having such a thin line between citizenship and expatriation is too dangerous. On one hand, choosing not to vote may be considered a serious enough act, but on the other hand there are dozens of reasons a vote can fail to be cast, and they would all need to be addressed before something as serious as expatriation is considered as a punishment.