What's the purpose of those unreadable writing formats in Word processors?

We know the common writing styles in these apps like Times New Roman and Arial. But then there are some writing styles that are completely unreadable as the characters don't resemble any sort of language. Sometimes they just turn into boxes while at other times they appear to transform into characters from a different, imaginatively constructed language that is funny, but still unreadable. So what purpose do these styles serve?