You are mistaken in your comparison. the subscription on patreon is a deal made directly between provider and consumer. Steem is not that, as a vote comes out of a shared pool of resources.

If it makes it easier to understand, see the Steem pool as a shared wallet between a group of people where any purchase made has an opportunity cost and affects all others in the group and their ability to purchase. If there is a 100 dollars in the wallet and someone wants to buy something for themselves with it, all others will have to go without. The downvote is a challenge of the purchase or perhaps, "the right to return" what was bought for some money back.