Democracy is a tricky thing. Make the bar for voting too low, and you give people the ability to swing an election by roping in folks who have no vested interest in the outcome... Make it too high, and you disenfranchise people who are probably already struggling with the site.
If you want moderators who represent the folks participating, you want to set the bar juuust high enough to catch folks who've actually participated. Hence the current reputation threshold.
But, I suppose we could also require you to own a horse and 50 acres of land.
In any case, it is imperative that we do our best to notify everyone who is eligible that an election is taking place and encourage them to vote. Failing to do so (and... We've failed to do so in the past) heavily skews the voting by focusing on the tiny clique of users who hang around the site all day and excluding those who drop in periodically to ask and answer questions. We're not doing that again.