I think Google prefers to support existing open source projects that are successful. Internally, a lot of Java engineers at Google use Eclipse, which is a great IDE for Java development. No need to re-invent the wheel, instead it makes more sense for them to contribute to the success of Eclipse.

FYI, Google also just donated $20K to the Eclipse foundation: http://www.thepowerbase.com/2012/09/google-donates-20000-to-...