The OSPF network type you use should be appropriate for the network topology in question. Yes, frame-relay is not something used very much any longer, but there are other network topologies that may use a network type other than the broadcast network type which is the default for Ethernet interfaces.
DMVPN is a prime example of a topology that can use different network types. You can see examples of how they are used in the following lessons:
I assume your question here has to do with the hub and spoke topology you mention in another one of your posts. You can see the response to that post here: