The problem is that the emojis appear different in different applications/devices. They're different enough that it can change the meaning of what you see, whic

The problem is that the emojis appear different in different applications/devices. They're different enough that it can change the meaning of what you see, which means that people end up using it in an application-specific way. But we already had application specific emoticons. They worked well, they work so well, that even with emojis in Unicode we still use application specific ones instead. Also, the default ones seem to always be ugly. Also also, the "weird human scripts" generally have a fairly long history of use.