Why aren't there female prophets? The reason there are no female prophets has to do with what a prophet must be exposed to. It is not because of any spiritually inferior status. In the same vein, there are no blind prophets, nor paralyzed ones, nor deaf ones, etc. It has to do with job function, not inferiority of the abled over the differently abled.
The first form of exposure that prophets are exposed to is abuse. Every father, uncle, brother, husband and son is obligated to protect their female relatives from being cursed, beaten or otherwise. In contrast, the prophets must expose themselves to the abuse of enemies but opposing them and tearing down false gods. Allah has decreed in His law that only males are obligated to bear public harm.
Second, prophets are obligated to lead their people in rituals, which involves being looked upon at all times. How to do salat and Hajj for example, are only known by the Companions constantly looking at the prophet. More specifically, the prophet leads the prayer and makes sujud, or prostration, before hundreds of men. This form of exposure too is something that Allah has not written upon women. Nor would any husband accept for the entire community to be constantly observing his wife and seeing her figure and back side.
Lastly, another form of exposure that prophets must be exposed to regards interactions. Prophets are examples in both deen and in everyday life. We know how the Prophet Muhammad peace be upon him ate, washed, slept and even more intimate details such as use of the bathroom and cleaning of sexual fluids. What woman would want this? How would this make her family proud?
In sum, the absence of female prophets does not imply inferiority of women in the same way that there are no blind prophets, and we know that neither the blind nor any other differently abled group are inferior to the able bodied.