Likes let me know that others appreciate or agree with what I'm saying. Its a signal of affirmation and/or an emotion. It also let's people thumbsdown or - if they don't like and want to convey that as signal in a quick way. Comments allow for dialog and clarity and are generally more useful than likes but also welcome trolls. Zaps let me know that something I did was worth value to you. Each of these has their place, and anyone that still thinks likes are useless or a form of fiat thinking is missing the forest for the trees.