I can understand a need to limit the amount that people vote, especially lower reputation users, but what about those who have a considerable amount (say 5000 or 10k and above) who are active participants? Shouldn't they be allowed to have unlimited votes, as they obviously know what they're doing to get that much rep?
It's so we don't spend all day on SE.
Stack Exchange wants to be for experts in the appropriate fields, and that means eventually kicking us off the site (gently) so we can go do that stuff. Part of the way it does this is by imposing limits on how much of certain things we can do on the site each day, so we eventually hit a ceiling. The ceiling is really high, but it's there.
This also keeps People Who Are Out Doing Things from falling insanely far behind in comparison to People Who Just Do Site Things, who otherwise would have the lion's share of influence over the site by sheer virtue of being around more. (It's still sometimes a problem, but it's not as big a one because --among other controls-- we have these limits.)