actually that is not true for ubuntu 16.04 there it will use the locale setting:

newly setup:

                                      List of databases
       Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
    -----------+----------+----------+-------------+-------------+-----------------------
     postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
     template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
               |          |          |             |             | postgres=CTc/postgres
     template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
               |          |          |             |             | postgres=CTc/postgres
    (3 rows)