Before SRV records existed, there was portmap for RPC services like NFS. Most system and network administrators hated portmap, still hate portmap, and the requi

Before SRV records existed, there was portmap for RPC services like NFS. Most system and network administrators hated portmap, still hate portmap, and the requirement for portmap was removed from NFSv4, at least for querying the target port of remote services. People are too accustomed to relying on firewall rules. We can't have nice things like SRV not because they're too difficult to use, but because they're too difficult to control with simple, static, external ACLs lower down the networking stack.