In many projects the Summary field does not make sense to the end users creating issues - as demonstrated by many Community questions.
The field can be easily removed from Create issue screen, resulting in errors at issue creation, with no intuitive instructions on how to fix this.
While there are ways to pre-populate it on the Create issue screen and then changing it behind the scenes, they all include custom JS, groovy scripting or 3rd party apps.
Having a simple setting in project configuration, called "Default summary" would make it easier for many admins to not include this field on Create issue screen.
This would remove the need for this documented workaround: