Right, but students are written into the grant. Ultimately, nobody gives a shit which post doc or student you put on a project; the assumption (often flawed) is

Right, but students are written into the grant. Ultimately, nobody gives a shit which post doc or student you put on a project; the assumption (often flawed) is that they're all the same as far as the modular budget is concerned. If they were special, the reasoning goes, they'd have their own F32 or T32 to work on the project.