Why do so many web apps automatically convert emoticons into emoji?

So many communication platforms convert expressions like

  • c:
  • :)
  • ]:)

etc. into emojis, e.g. ?,?,?.

I find this so annoying every time it happens. If I want to send an emoji, I will just send the emoji.

The text faces are often cuter, less garish, and what I (and every single one of my friends) intends.

What's the incentive for companies to make these automatic substitutions?

Companies pay someone to implement this "feature", I wonder what the research is that claims most users like having their messages manipulated as they send them.

All I can find are people ranting about it, and posts online of people asking how to stop these automatic substitutions.

So yeah, why is it good user experience (or at least, why is it so commonplace) to swap out the user's emoticons with emoji?