I guess it's based on the fact that the Battle.net people have largely grown up now, perhaps outside of their intended demographic...
But with that said, I really do fail to see the point in renaming it. Battle.net is instantaneous brand recognition and personally, comes to me as having a fair degree of respectability. It's solid, it's backed, well-supported and useful.
You say Gamespy, maybe some people know it. Say game ranger, some might know it. Name hamachi or ESO or these other engines, people might know it. Anyone who's part of the culture, however, KNOWS Battle.net. It's a staple.