I wouldn't take using something else as them not thinking CF is suitable, look at these very forums. Adobe could easily have written their own forum software but instead decided to lumber us with this shonky Jive malarkey.
Many of the sites they are using might well be powered by various suitable CMS's behind the scenes, and not many of these are based on CF; therefore Adobe are stuck using ASP, PHP or whatever.
If they started using Silverlight I'd completely agree with you and it would look very poor on them, but web technologies are so varied that sometimes CF just isn't the tool of choice, that doesn't make it a bad product.