Using stickers well is also a form of eloquence, and of demonstrating empathy. They're often commentary for just-received messages, i.e. it's a way to say "I go

Using stickers well is also a form of eloquence, and of demonstrating empathy. They're often commentary for just-received messages, i.e. it's a way to say "I got what you just tried to say" by picking the right sticker (individual well-known sticker types - such as poses or facial expressions found in many different packs across different characters - become tropes/memes). And people also tend to appropriate certain characters, so it becomes a way to maintain an identity within group.