So, why might a customer want to run their own nameserver?

Often times customers just want to cache their DNS entries locally so that they can have faster DNS response times.

The way this is done is though configuring a forwarder with caching. There are a few lightweight ways to do this.

We have a KCS article which covers this as a whole:

Best practice for DNS caching in RHEL
https://access.redhat.com/solutions/2189381

The tools mentioned are:

dnsmasq:

How to configure DNS caching server with dnsmasq in RHEL
https://access.redhat.com/solutions/2189401

unbound:

How to configure DNS caching server with unbound in RHEL
https://access.redhat.com/solutions/4448031

systemd-resolved:

Is systemd-resolved available and supported on RHEL 8 or RHEL 9?
How can be configured systemd-resolved.service as DNS cache?
https://access.redhat.com/solutions/5647181

The heavier, more robust BIND DNS server:

Configuring BIND as a caching DNS server
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/managing_networking_infrastructure_services/assembly_setting-up-and-configuring-a-bind-dns-server_networking-infrastructure-services#proc_configuring-bind-as-a-caching-dns-server_assembly_setting-up-and-configuring-a-bind-dns-server

And lastly, nscd (again, not recommended):

How to configure nscd daemon for naming resolution?
https://access.redhat.com/solutions/2187751

I would recommend walking through each tool to set up DNS caching on them to see their basic configurations and differences. They are not difficult to configure.