Compare online communication to in-person communication.
In person we might have many people engaged in a conversation at the same time. It would be rude and unproductive if everyone interrupted routinely just to say, "I agree," or something equally as simple. In stead, we all learn to, "read the crowd," as it were, by watching the looks on the faces around us, or reading body language. Smiling and nodding along means either that person agrees, or they're not actually paying attention but don't want you to know. That's the like button.
As digital communication has evolved, we've invented things that help us emulate in-person communication more- likes and emojis and such, that stand in for the nonverbal parts of conversation. In this forum, that looks like the reaction button on posts.
In social media, though, the drive is more interaction WITH THE SITE/SERVICE in order to propel investment, and users are the means of doing this. The, "likes," are constantly tallied, and you only see the things that OTHER PEOPLE liked the most frequently, or the things that got everyone angry so they actually commented because there's no, "dislike," button, and you can chose to see more of how other people feel if you like.
Anyway, yeah, I like the, "like," here because it has no more or less effect than a polite nod in passing: I see you, I appreciate that you shared, and I have nothing to share on the topic right now. It emulates the vast majority of human interactions quite effectively.