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Liquid rockets usually use a propellant pair of fuel and oxidizer. I've seen some rockets from 1960's that used LOX/UDMH as propellant pair but why they are not used any more although it is mentioned that LOX/UDMH has higher performance than N2O4/UDMH but N2O4/ UDMH is used abundantly.
If there are any rockets with LOX/UDMH kindly mention them.
N2O4/UDMH is the choice if you need a non cryogenic storable hypergolic fuel. But UDMH is toxic and carcinogenic and should be avoided if possible. UDMH is also corrosive. LOX/UDMH is not storable (cryogenic LOX) and not hypergolic.
There are a lot other fuels to be combined with LOX and they are not toxic or carcinogenic and thus easier to handle. There are combinations of LOX with higher performance than LOX/UDMH.
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.
