The reason you go with UDMH/NTO F/O pair is storability, i.e. the ability of your rocket or missile to be stored, fully fueled straight from the factory, in a silo or stand on a launch rack for an extended amount of time, possibly years or even decades, and ready to use at a moment's notice, and spontaneous combustion upon contact with no ignition, meaning no fireplugs or glow wires or squib or matches needed, or deep space mission, e.g. main propulsion engine on the Cassini probe, where any cryogenic propellent eventually boils away. There's simply no other advantage to hypergolics if these two scenarios are not your concern. Going half-measure, either UDMH/LOX or kerosene/NTO defeats the only reason for choosing hypergolics. The weird combo you mentioned is mostly a product of its time when rocket propulsion engineers are making the switch from more primitive stuff like RFNA or H2O2 and trying out new combos. As soon as the UDMH/NTO pair was found and demonstrated reliability all other combos were simply dropped.