standalone profiles don't pre-fill user info; error in "edit" mode

When filling out a standalone profile in "create" mode, logged in users' existing info does not pre-populate the fields, like civi does with events and donations. When filling it out in "edit" mode, non-logged in users get the following error:

> No user/contact ID was specified, so the Profile cannot be used in edit mode.

It would make sense to fill out logged in user info in "create" mode, to reduce the amount of retyping and minimizing room for user error. Alternatively, the "edit" mode should fall back to "create" mode functionality if the user is not logged in, instead of giving an error that blocks the user from using the site.