Diversification makes sense in a preservation context, where any asset you have could devalue by a near-arbitrary factor - and then it only matters because the utility of going near 0 assets is really really negative, so you try to steer around that by not letting one catastrophe sink you.

When handing out goodies, there is no such extreme penalty for it ending up worthless. It would be bad, but since it's only linearly bad, that's taken into account fully by taking the expected return.