Why are there emojis in commits?

I've seen repo's use them as a way of categorising the type of commit (don't have an example at hand), which could be a good use if used consistently and the categories fit your workflow.

After spending a great deal of time and effort in tracking down some obscure bug and fixing the code, a bit of venting using emojis is almost a reflex action.

Why do you post a random question with no examples, context, or explanation as to why it's interesting?