The reason is because a portion of it is taken by the people who upvote, especially whales. They help you get more value, you keep 50%, then of the 50% left, you can end up keeping 50% more of that 50%, or 25% more of the 50%, etc., but the voters get some of the value they created for you. You don't get to keep it all. The upvoters helped to create the value you get, and they get part of the value generated in the payout for doing so, so everyone win. You win the most though, since if they didn't upvote you, you would not even of gotten what you got. Hope that helps to understand things. Peace.