Why political scientists? Why not lawyers? After all, in most governments elected represenatives are responsible for the passage of legislation - i.e laws. Given that their entire profession is about drafting documents, debating or ensuring compliance with the law, wouldn't they be better suited? A barrister/advocate/trial lawyer should theoretically at least have some grounding in public speaking and debating - I don't believe this is a skill that is trained in political scientists.
The answer is fairly self evident: Democracies are meant to represent the entire cross section of society. If only political scientists were electable then they would only represent the interests of political scientists. I mean it's not like we've ever had situations where small subsets of a population hold power and use it to support to their own interests to the detriment of everyone else. Pretty sure that's like never happened.
I'm pretty sure though that this question is asked on an almost daily basis by people of a variety of vocations and partisan persuasions which can be sublimated down to the form of "Why aren't there more people like me in power, and less like them?"
Since one ought to guess that political scientists would have broadest
knowledge of history and empiricism of political behavior, whereas
people from totally unrelated fields might be more susceptible to
"favoritism" or being unable to learn from history and empirical
research regarding different configurations.
This is essentially like arguing that sports commentators should be good at a particular sport because they commentate on it a lot. There's no reason why political scientists would be any more or less "moral" than any one else.
I'm going to go out on a limb here and suggest you're a PolSci undergrad?