Update Scala Version to Some Version on Debian/Ubuntu/Mint Linux Distrubtions via CLI

updateScalaVersion.sh

# Author: Daniel Gordon
# License: MIT
# Created: 10/28/2016
#
# Mini Script for Updating Scala to some Scala version
# Does not update SBT. Just Scala.
# See <http://www.scala-sbt.org/0.13/docs/Installing-sbt-on-Linux.html> for upgrading SBT
# This is for Debian/Mint/Ubuntu distributions only
# 
#   TO USE AS A SCRIPT:
#   Download this as a file and rename it so updateScalaVersion.sh to use it as a script
#   Comment out the first line of code and uncomment the line above it to use as a script like this:
#     ./updateScalaVersion 2.11.8
#   Don't forget to run "chmod +x" on the script, and you will likely need to run it in `sudo`
#   Running as a script is UNTESTED as of this writing.
# 
#   ALL COMMANDS NEED TO BE RUN WITH "SUDO"

# scalaVer="$1"
scalaVer="2.11.8"
apt-get remove scala-library scala
wget www.scala-lang.org/files/archive/scala-"$scalaVer".deb
dpkg -i scala-"$scalaVer".deb
apt-get update
apt-get install scala

When dpkg -i is already installing scala, why is apt-get install scala also required?