How do you delete a contact field that is in bold?

My goal is to free up contact record field space. My company's instance has many bolded contact fields that don't apply to our business model. I cannot delete these unused, nonapplicable fields because the delete button is greyed out and inoperable. It seems like these are system standard fields, but they are simply taking up space.

There are no dependencies on most of them. How do I delete these contact record fields? We will never use them due to our business model.