What is wrong with Mircosoft providing an obfuscation (or better) tool for Windows XNA games?
Microsoft has a limited amount of manpower to put onto any one project. If they had additional manpower, I'd much rather see it put onto things like a faster compact JIT, or the ability to stream runtime-generated sound -- things that actually change what you can do. After all, most of the MS people know that obfuscation doesn't really work, too, so they're probably reluctant to spend any time on something that doesn't actually add much value.