[RTTY] A question on the history of the major RTTY contests

[Rudy Bakalov]

In the past week or so I had two separate situations in which I got the distict impression that CQ WPX RTTY and CQ WW RTTY are considered "separate" events from their respective CW/SSB brothers. So I was wondering why. Is there a historical reason, such as being sponsored by different sponsors or anything else? It is a bit strange.
Rudy N2WQ