There are several reasons why you might want to create a default value:
If one answer is much more common than others
If you'd like to use a field in a formula (especially if it's in a conditionally-triggered section)
You can select a default value for any field when you're setting up a workflow.
Just click the Advanced Settings option you see below each field in the Edit view, and set the default value. It can be text, a number or a multiple choice answer.
If you'd like to set a whole group of fields to be pre-filled in multiple workflows, check out our Organization feature and see if it's right for you.