This is where Emoji came from. Imagine a late 1990's cell phone with the 12 standard buttons, and having to send text messages to someone in Japanese. How do you use those 12 buttons to select from thousands of Kanji symbols?
Don't try and be an amateur linguistic historian, when people are alive today that sent SMS messages in the mid 1990s. Also, the history of emoji is in Wikipedia.
So what's the real story? Someone at NTT Docomo wanted prettier emoticons. Then once they had that, they decided to shove all their icons into this new dingbat font for ease of use. Softbank wanted feature parity, so they did the same. Then later the two fonts were shoved together, and so we have the unholy union that gives us ðY"' and ðY--, âoe'ï and ðY-, and my favorite ðY" and ðY"Z.