Please add these! I use them a lot on the desktop version of Scrivener and would like to be able to use them on iPad as well if possible.
Unfortunately this is something you would need to post as a request to Apple’s feedback area. The rich text editing engine that they provide completely lacks listing tools. We threw together a very simple alternative so that there would be something, and that is what you see.
This is one big reason for why I use Markdown, personally. You don’t need software to develop complicated and fancy features to get stuff like lists, when all you need to make a list is an asterisk key, a tab key, and a text editor capable of storing ASCII characters. I can compose complex lists (more complicated than what even the Mac RTF editor provides) using a PalmPilot from the '90s, or even WordStar—or Scrivener for iOS.