Why does MSBuild use only one core, while VS.NET uses all the kernels available on the same .sln?

Our solution consists of 20 .vcproj files. With the exception of the main program, most of them are independent libraries that depend only on their own unit tests.

When we create this solution in VS.NET, we notice that VS starts several VCBuildHelper processes and effectively uses all available kernels. However, when we run our daily build scripts implemented using MSBuild, we notice that only one core is used.

We added / maxcpucount and / p: BuildInParallel = true, but it still does not work.

Any help is appreciated.

Thanks in advance!