Is there a risk some people on this thread are mixing up DKIM and DMARC?
DKIM = proving that an email was sent from a specific domain using cryptography. Good for spam fighting and deliverability.
DMARC = telling receivers how to handle mail that fails authentication.
DMARC is primarily useful for large, complex organizations where email admins may not be aware of everyone inside the org who is sending mail that advertises the domain in the From header, or organizations that might be targeted by impersonation attacks (e.g. phishing). Being able to tell recipients "yes we absolutely have our act together so feel free to reject or spamfolder unauthenticated email" is great for killing phishing campaigns, and being able to request reports is great for finding that one sales org that signed up for a guerrilla marketing SaaS that's impersonating them.
But for small personal domains the value isn't that high.