I agree with both points, but opening them consists of a number of steps: it's not just throwing the code over the wall: Has it been cleared by Legal? Does it expose any internal/company confidential information? (In particular, in the build system) Does Nokia have the right to open the source code up; or is some potentially owned by a third party? Has it been reviewed for any inappropriate comments in the source? ... So releasing existing apps will cost Nokia real time & money; despite how sensible it seems to be (and I'd love to fix one or two bugs rather than help Mohammad in the effort to port the existing media player to Qt in an open source way)
When it comes to product development the guys deciding on the Nokia investments and the plans to convert them into benefits conclude that having a Nokia proprietary layer is better for business than not having it. Looking at the market and at the business results of companies shipping devices with 100% free software I can't deny that they have a point.