Not everyone uses Outlook and generally speaking, if you don't use Outlook you shouldn't install it. Office updates have a habit of installing updates for Outlook, even if you are not using it, and then setting Outlook as the default email client, so not installing Outlook (or uninstalling Outlook later) is recommended to avoid the annoyance.
You nay also need to use this method if you are installing another version of Office and want to keep your current version of Outlook.
When you are installing Office, don't use the default install - which is identified by the big Install Now button (it may be labeled differently in older versions of Office).
Choose the Customize button and change Outlook (and any other applications you won't use) to Not Available. I don't recommend changing the settings for many of the optional files unless you know exactly what the file does; you might soon discover that features you want to use don't work as expected.
After clicking Customize, a screen comes up with a list of the Office applications.
In the case of Outlook, you want to select it and set the entire program to Not Available.
Repeat for any other application your don't want to install then complete the installation wizard