It is well-known that the partition function can consistently be factorized from the canonical equilibrium distribution obtained through the maximization of the Shannon entropy. We show that such a normalized and factorized equilibrium distribution is warranted if and only if the entropy measure $I \{(p_i)\}$ has an additive slope i.e. $\partial I \{(p_i)\} / \partial p_i$ when the ordinary linear averaging scheme is used. Therefore, we conclude that the maximum entropy principle of Jaynes should not be used for the justification of the partition functions and the concomitant thermodynamic observables for generalized entropies with non-additive slope. Finally, Tsallis and R��nyi entropies are shown not to yield such factorized canonical-like distributions.

7 pages, 2 figures, Accepted in Physics Letters A