But an upvote doesn't mean "I like this". It means you judge the post/comment to be high quality. There's a correlation for sure, but quality is a holistic judgement based on context. It measured by the same spectrums as downvoting: to what extent is the post/comment relevant, original, funny, entertaining, informative, rule-abiding, respectful, etc. We don't need separate buttons for all of these, the voting buttons just wear many hats. You're generally going to think more highly of stuff you agree with or that makes you happy, but accurate bad news and unpopular opinions can still succeed score-wise despite these disadvantages.