I was reading privileges on this page and I learned that you can see vote counts and expanded usercard at 1000 reputation points.
Why it's so expensive to obtain this privilege ?
According to Meta.SE:
because it's "expensive" to view the vote count (in terms of running the query)
That is, with a vote table as massive as StackExchange's, allowing all users to make requests to view vote totals would put too much stress on the system. The rep requirement decreases this stress.