As someone that wasn't ever particularly active on Reddit, I didn't even know that was a general attitude there. I've generally never understood the hate that some people have for emojis, though. They have their place in certain circumstances and can make communication easier in general sometimes, especially in private, more personal conversations. Tone can be so hard to decipher through text.
Then the kids themselves started taking an anti-emoji stance, perhaps after their teachers started using them. Minimalist use is still fine, but excessive use has always been kind of annoying, and is just not a good idea if you want to get your point across in a forum with a broad audience.