Then again, when you look at the performance of your typical pension fund or university endowment, and then see the actual incentives of the people managing the money (as there's ultimately managers there looking for their personal best interests), then you see that said argument one could make is not exactly going to do well empirically.

The main reason we are seeing private equity now being offered in 401ks isn't that it's going to be great returns for your average mostly-self-directed worker, but because those managing private equity believe they will make more money if they managed more capital. There's no guarantee that they are making any choices there that provide good risk-adjusted returns. But the managers sure would be making more on fees.