As a whale my votes tend to hand out between $50 and $100 worth of rewards with every vote. This how I view voting at this point in time.
There is not enough content
The number of posts that are worthy of $50 or more is vanishingly small. If I only voted on the highest quality posts then my voting power would be much higher and they would probably receive $500 per vote. That said, these posts get enough support from other community members that they receive thousands of dollars anyway.
By spreading my votes around to many people it builds the platform by encouraging more content.
People matter more than content
Attracting people matters the most while Steem is young. Any time I see a honest post from someone new they get a $50 upvote. This will give them more influence in the future and gives them a taste of what is possible with Steem. After their first "hit" they are more likely to come back for more.
Precision is not necessarily better
As a voter it is very difficult to make fine grained subjective valuations. I can see some benefit for having the ability to vote with different weights, but I am not sure it would really improve the platform. The feeling someone gets when they are randomly "over tipped" for a small job can be addictive. This creates a lottery effect where posters know that they could get $50 for something as simple as posting a link to answer questions from a new user. Often they don't see anything, but occasionally they get a big bump and that makes all the difference.
Equal Pay for Equal Work doesn't Work.
What if I told you that we developed a perfect AI algorithm that would rank and score every post based upon the exact value it brings to the platform. All of a sudden the payouts earned by many top posters would fall from thousands of dollars to hundreds of dollars. Most other content would see payouts well under a dollar. As someone participating in the system you would be guaranteed to get paid exactly what your contribution is worth.
This would make the platform much less interesting. People come here for the chance to get paid much more than their effort is worth. It is the oversized payouts that give people hope and drive the most engagement.
Vote for everything with any value
As a whale I choose to vote often. This spreads my power around and effectively lowers the payout-per-person. I am afraid that everyone is so worried about curation rewards that they are ignoring the bigger picture. You should vote for everything you think adds value to the platform and not restrict yourself to 20 votes per day.
Response to Proposals
Many people have been making proposals on how to enhance voting and to solve the problem of "passive whales". The truth is passive whales are best "not voting". When you refrain from voting you delegate the curation task to everyone else.
Others have proposed that whales should be able to proxy their voting power to others. This concept has some potential if it is kept simple. My feeling is that this feature would add complexity that only benefits a hand full of people.