Yes, even Cologne.
And about the popularity aspect, I knew, this would pop up...Yes, You could do more "advertisement", yes, they have "the potential" to be interesting for the public, yes the "challange of keeping them" shouldn't stand in the way of keeping them etc. etc.
But unfortunately, this is also true for dozens of other species, may it be Mountain tapirs, Kagus, Ratels, Snub-nosed monkeys, Proboscis monkeys, Goliath frogs, Aardwolves etc. etc... The bottom line is that many modern zoos, also due to international breeding programmes, rather focus on less and less species that are easier to get due to an already existing zoo population, as well as being easier to keep while having the same or similar effect on visitors, instead of (re)introducing more species to their zoos; the times of animal collections are almost over in many zoos. In the case of the saiga, that means that especially blackbucks are filling in their position as "zoo antelope"-and most visitors of Cologne Zoo surely won't notice that "that weird antelope-thingy" is missing and has been replaced.