CL packages

bar.lisp

;;;; Path: ~/quicklisp/local-projects/foo/src/bar.lisp

(defpackage foo.bar
  (:nicknames :foo.bar)
  (:use :cl)
  (:export :my-function))
(in-package :foo.bar)

;; :arrows is not imported, but I can still access it
;;
;; What is the point of :USE'ing or :IMPORT-FROM it in that case???
(defun my-function ()
  (arrows:-> 2 (+ 40)))

foo.asd

;;;;
;;;; Consider that we have the following system in our Quicklisp's local-project (e.g. ~/quicklisp/local-projects)
;;;;
;;;; Path: ~/quicklisp/local-projects/foo/foo.asd

(defpackage :foo-system
  (:use :cl :asdf))
(in-package :foo-system)

(defsystem :foo
  :name "foo"
  :description "Foo system"
  :version "0.1.0"
  :author "John Doe <john.doe@example.org>"
  :maintainer "John Doe <john.doe@example.org>"
  :licence "BSD 2-Clause"
  :long-description ""
  :homepage ""
  :bug-tracker ""
  :source-control ""
  :long-name ""
  :depends-on (:arrows)
  :components ((:module "src"
		:components
		((:file "bar")))))

repl.lisp

CL-USER> (ql:register-local-projects)
NIL
CL-USER> (ql:quickload :foo)
To load "foo":
  Load 1 ASDF system:
    foo
; Loading "foo"
To load "arrows":
  Load 1 ASDF system:
    asdf
  Install 1 Quicklisp release:
    arrows
; Fetching #<URL "http://beta.quicklisp.org/archive/arrows/2018-10-18/arrows-20181018-git.tgz">
; 4.95KB
==================================================
5,067 bytes in 0.00 seconds (4948.24KB/sec)
; Loading "arrows"
[package arrows].
To load "foo":
  Load 1 ASDF system:
    foo
; Loading "foo"
[package foo.bar]
(:FOO)
CL-USER> (foo.bar:my-function)
42
CL-USER> 

When ql:quickload'ing the :foo system the :arrows dependency is being downloaded, built and loaded, which in turn makes it readily available for our foo.bar package to use without having to :use or :import-from it.

What is the point of of using :use or :import-from within the defpackage definition, if the dependencies are already loaded and available?