Chief of Security. Manages shipboard security, leads armed response teams, interrogates intruders, etc. Sometimes even controls ship-mounted weapons and/or the armory, depending on the era and ship/installation. We had Reed in ENT, some minor one-off guys in The Original Series, Chekov in the TOS movie era, Yar and later Worf in The Next Generation, Odo in Deep Space Nine, and Tuvok in Voyager. Obviously, we know that Abrams and his crew didn't want to tamper too much with the classic elements of TOS in casting for the Kelvin Timeline movies. That said, what could be an in-universe reason the Kelvin Timeline Enterprise is never seen to have a Chief of Security in any of the three movies thus far?