Yes, optional cover letters are really optional. However, including a cover letter will give you a huge advantage over applicants that choose not to send one. Cover letters strengthen your job application because they allow to do things a resume can’t, such as:
- Showcase your personality
- Display your enthusiasm for the job or company
- Provide evidence of your noteworthy accomplishments
- Explain work gaps or other issues on your resume
So if you have time to write a cover letter, your should always make the effort.