Why is the electrode potential for a cathode positive?
The question: Why is the electrode potential for a cathode positive?

Since question didn't directed to what kind of cell, the answer is it is not always positive:

As M. Farooq clarified, cathode is where reduction is happening in a cell. Thus, in Galvanic cell it is positive as the reduction reaction, $\ce{Y+ + e- -&gt; Y}$, happens. The electrons needed for this purpose came from the anode. However, in an electrolytic cell, electrons from an outer source (e.g., a battery), flow to the negative end where the reduction reaction, $\ce{M+ + e- -&gt; M}$, happens. Thus, the cathode is negative here.

Edit: I agree with  Poutnik's comment below. Accordingly, it may be better to say cathodes are more negative than anodes in electrolytic cells and more positive than anodes in galvanic cells. As more positive does not mean positive and more negative does not mean negative. The convention of marking positive and negative cell contacts is good enough for every day life, but it says nothing about the sign of electrode potentials either with respect to free electron or SHE (e.g., relevant half-cell reduction reaction's potential may carry positive or negative sign, based on the corresponding reaction).