- You want a certificate with a lifetime longer than Let’s Encrypt’s limit of 90 days, which might be convenient if you need to install it on a server or device that doesn’t support automatic renewals with the ACME protocol.

- You want a certificate for a domain name that Let’s Encrypt wouldn’t be able to validate automatically, such as one not used actively on the public Internet.

- You are required by law or contract to include a validated organization name, locality, etc., in the certificate, or to use a certificate that meets some other standard that Let’s Encrypt’s don’t.

- You want more control over certificate issuance than Let’s Encrypt provides. For example, an organization might arrange with its chosen CA to require specific validation procedures, such as approval by a designated employee, and then publish CAA records in DNS instructing all other CAs not to issue certificates for its domains.