They already have some romanizations like Pinyin that are largely phonetic.

But take something like "mao". Without any accents to indicate the tone, that could be:

  * 毛 - like a dozen distinct meanings
  * 猫 - a few meanings, but mostly "cat"
  * 冒 - half a dozen meanings
  * 昴 - one meaning
  * 懋 - a few meanings
  * 帽 - a few meanings
  * 貌 - a few meanings
  * 牦 - one meaning
  * 矛 - one meaning
  * 铆 - a couple meanings
  * 锚 - one meaning
  * 贸 - one meaning
  * 茂 - two meanings

When someone uses a romanized keyboard to type "m", "a", "o" you've got like two dozen possible characters that becomes. If you're trying to figure out from context which one the person might be intending, you need to look at like 60 different possible meanings in context and figure out which characters are most appropriate. And that's given the previous several things they've entered have been narrowed down to one character, but likely still have several meanings.

A lot of (I'd dare say most?) Chinese people do use romanized input (the alternative I've seen is very slowly drawing out each individual character on the screen), but whether the keyboard sees you type "I have a cute... mao" and decides you want 'anchor' or 'cat' has a huge impact on day-to-day usability for people actually using it.

The written language is vastly more complicated than the spoken one as far as I can tell. A syllable that can have 60 meanings is relatively easy to figure out in context, but when written the meaning has to be made explicit. As a really basic example, "ta" is both he and she. So they just don't have masculine and feminine pronouns, right? Wrong. 他 is he, 她 is she. These are said exactly the same so even given accents to indicate tone they're romanized identically. But when written, the distinction is made.

And if you make a mistake somewhere in all of this?

Well, baba (爸爸) is dad. baba is also poop (㞎㞎).

Wo ai ni, baba. I love you, poop.