Many technologies rely on being able to programmatically modify DNS. For example, the DNS-01 challenge is required for Letsencrypt wildcard certificates. Letsencrypt certificates have to be renewed after at most three months, so this is something that warrants automation to avoid lapsed certificates.
Another widely used example of automated DNS is “dynamic DNS”, where you associate a domain name with a host that has a frequently changing IP address. Although there are many services offering free dynamic DNS, most don’t combine it with DNSSEC and few give you the ability to use your own domain or handle many other record types besides A and AAAA.