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There is set amount of steembucks that get generated every day. That is where the upvote money comes from. When your vote has low value, voting has minimal impact on the overall pool. When your vote is worth a lot, it is a drain on that pool. By the time your posts are generating lots of upvotes from other people. it is just sort of poor taste to keep upvoting yourself. This is not a hard rule or even something I made up, it is what I have gathered listening to others here.

Finally someone who gets it.