It probably was done for security, the r- utilities being the security pitfalls that they are. It's not defending against attacks. It is, in fact, defending a

It probably was done for security, the r- utilities being the security pitfalls that they are. It's not defending against attacks. It is, in fact, defending against exactly you, a person who comes along and wants to use the r- utilities. It's a compromise between (most likely) "We mustn't use r- utilities on our LAN any more, and must remove them everywhere." and "This is SCO Unix; it's not even OpenServer.".