The actual problem, is many times, it's irritating when we vote and receive nothing. Plus, there are people who might vote from different IPs (if I am correct, you can vote twice if from different addresses). Also, giving the chance to many people to get a small voucher for supporting the server is not unfair. I am not just saying because I want to benefit my self, I think this idea would bring tons of players and, therefore, donators. Not everyone votes everyday, but this could give them motives. In addition to the fact that even if you meet the 0.1 chances of getting a fly voucher it only lasts for an hour, so these rewards seem quite silly and don't motivate people to vote daily.
The current system works fine. Why fix something that's not broken?
~ @Muunkee
I never called the voting system "broken". If you read more carefully, you'd understand that my point is (as I say above) that vouchers would motivate people to vote and give the chances to more than just one person to get a nice reward when they are worth it. So if I were to characterize the system, I would rather describe it as "discouraging". Even though (also stated above) it doesn't give us anything sometimes and there isn't even a list with the top voters to let us know where we are