There isn't really much need for internal security. The crew is small and even if they fought amongst each other, the corporations in charge of putting together the crews would only use that as more fuel to the reality-tv fire they're stoking back in the Milky Way, almost to the point of encouraging squabbles (possibly even to the point of placing specific members of intergalactic teams against each other). As far as external security goes, it's a scout ship. Even if they were to come across a hostile species, they would be stupid to engage in any form or fashion, and the number of actual "away party" type missions are likely to be few and far between.
It is a typical role that is, in some ways, missing from what we have, but I don't think the scope really justifies having a more military-minded character.
