Incomplete/unlocalized keyboard for <input type='number'>

Put the following code on a form on a web page
<input type='number' value='1234.5678' step='0.0001' name='frmVal'>
and browse to that web page.

Entering negative numbers is not possible: there is no minus sign on the keyboard.

I'ts also impossible to enter the decimal separator character if it's different from a dot.
To reproduce switch your phone to a language which uses comma as decimal separator (i.e.: italian).
You will notice that the value will be correctly rendered to 1234,5678, but the keyboard will only let you enter dots and not commas.