Optimal Strategy

In general, the player should stick when the expected value for sticking is larger than that of hitting. The expected value for sticking with the dealer has d and the player has p is r^p(d).

What's the expected value of hitting? In the above example, it was $\sum_{p'} \Pr(p'\vert p) r^{p'}(d)$.

Why is this not the answer in general?