Jetpack Compose has an Icon composable where I can access an imageVector. See example below.

Icon(
     imageVector = Icons.Rounded.Email,
     contentDescription = "Email Icon",
)

Why can I not access all icons listed in this Material Icons library through this imageVector. For example, "wifi_off" can't be accessed. There is a very limited library accessible via imageVector

As described in the doc:

androidx.compose.material.icons is the entry point for using Material Icons in Compose, designed to provide icons that match those described at fonts.google.com/icons.
The most commonly used set of Material icons are provided by androidx.compose.material:material-icons-core.
A separate library, androidx.compose.material:material-icons-extended, contains the full set of Material icons.