What's wrong with iphone handwriting?

Are you sure that simplified Chinese handwriting is turned on in Settings and International Keyboard?

There must be handwriting,

But you said, "clicking on that earth symbol is just a numeric keyboard and a standard keyboard."

Either the hand is big, or the screen is drifting, and the earth icon (input method switch key) is clicked, but actually the 123 icon (English and numbers, character switch key) is pressed.

Either you chose the wrong place, not the place where the SMS content was entered. This phenomenon will only happen in places such as inputting numbers/websites, because Chinese input is not allowed. (The virtual keyboard of iPhone is different in different regions! )

Look carefully first. If you have any questions, you can Baidu hi me, or send pictures.