cloud-init from trusty is already depending on python-serial. Why does it need to get added explicitly?

Package: cloud-init
Priority: extra
Section: admin
Installed-Size: 964
Maintainer: Scott Moser <email address hidden>
Architecture: all
Version: 0.7.5-0ubuntu1
Replaces: ec2-init (<< 0.5.3)
Provides: ec2-init
Depends: cloud-guest-utils | cloud-utils, ifupdown (>= 0.6.10ubuntu5), procps, python (>= 2.7), python-requests (>= 0.8.2), software-properties-common, debconf (>= 0.5) | debconf-2.0, python (<< 2.8), python:any (>= 2.7.1-0ubuntu2), python-cheetah, python-prettytable, python-oauth, python-serial, python-configobj, python-yaml, python-jsonpatch
Recommends: eatmydata
Conflicts: ec2-init (<< 0.5.3)
Filename: pool/main/c/cloud-init/cloud-init_0.7.5-0ubuntu1_all.deb
Size: 190622
MD5sum: cc0d636ccbdff6f6969505eb33da29cc
SHA1: 05aef5df1b3b7c0f4612b4b08cc5b8931efbf43f
SHA256: e669b7b7bc7176219f013c1895e8662640e25e70f7fa0e76ba8333b9244fa397
Description-en: Init scripts for cloud instances
 Cloud instances need special scripts to run during initialisation
 to retrieve and install ssh keys and to let the user run various scripts.
Description-md5: 8719ef0e4178017b7147590b1fde082e
Python-Version: 2.7
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu
Supported: 5y
Task: cloud-image


ubuntu@foo:~$ dpkg -l python-serial
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                            Version                      Architecture                 Description
+++-===============================================-============================-============================-===================================================================================================
ii  python-serial                                   2.6-1build1                  all                          pyserial - module encapsulating access for the serial port
ubuntu@foo:~$ sudo apt-get remove python-serial
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libfreetype6 os-prober
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  cloud-init python-serial
0 upgraded, 0 newly installed, 2 to remove and 99 not upgraded.
After this operation, 1,410 kB disk space will be freed.
Do you want to continue? [Y/n] ^Cubuntu@foo:~$ dpkg -l cloud-init
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                                            Version                      Architecture                 Description
+++-===============================================-============================-============================-===================================================================================================
ii  cloud-init                                      0.7.5-0ubuntu1.5             all                          Init scripts for cloud instances