rails rake db:migrate pg_dump docker

pg_dump

#!/bin/bash

# rake db:migrate tries to connect to dump local postgres using pg_dump but
# you are using a docker instance? try saving this script as pg_dump somewhere
# in your PATH with higher priority

orig_params="$@"
volmount=""
while [[ $# -gt 1 ]]
do
    if [ "-f" = "$1" ]
    then
        volmount="-v $2:$2"
        shift
    fi
    shift
done

docker run -it --rm $volmount --net=host postgres:9.4 pg_dump -h localhost -U postgres $orig_params

Why does rails do this and ignore the remote host specified in config/database.yml?