A three-terminal device like this is missing an important extra degree of freedom, namely the ability to put some R's in the bottom emitters to trade off noise for bandwidth. If the 1:1 versions are used for the typical op amp input stage they add significant noise. Also if you look at the specs they aren't very impressive for current accuracy, considering that these are monolithic parts.
Why are parts going away? Of course it is at root economics, but behind the lower to zero volumes of parts sold is the general decline in any real knowledge of analog design.
I'm feeling unusually curmudgeonly today, but...
A former client now is using DSP EQ everywhere in new products as there is no one left there who knows how to design successful analog EQ. The speaker guy who uses the gui-based DSP card to flatten his new response now gets what he wants immediately without having to deal with the electronics people, which works for him. The fact that the resulting product costs more is important, but the time-to-market issues and management brownie points dispensed for adhering to schedule are overriding. And then the blurb writers can throw in a few more "digital" adjectives in their poop sheets. And we all know digital is better for everything, right?
"Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea." (HHG to the G).
Of course digital has its place, and refinements and extensions of it are to be respected and honored. And sales and marketing departments still have stringent requirements, like a two-drink minimum.