I can see know way to use the CREATE DATABASE FORM to create a database from anything other than the default database skeleton-- 'template1'

This functionality would be handy for super-users who wish to let regular-users create databases loaded with different default functions/extensions.

ie:
templatePostGIS
-- Would contain postGIS functions

while:
template1
-- Would contain the standard template (no functions)

By adding a CREATE DATABASE FROM TEMPLATE option on the CREATE DATABASE FORM, a super-user can stay out of a regular-user's database creation process.

Or more specifically, a regular-user does not need a super-user to alter any newly created database to include any of the functionality previously loaded into a template database.