The reason why is that I do not always want the glowy look of HIE / IR820. Even if I could still buy it, I would prefer Rollei IR400 for most of what I do, it is sharper, easier to deal with and frankly, it is incredible for rock, ice, water and sky.
I use IR400 strictly with a R72 filter and it prints utterly fantastic. Now I have gone though about half a brick of SFX200 in 120 and have yet to hit my stride with it. It definitely feels like a slight step down in terms of the bold and sharp IR effect of Rollei but I need to work with it some more, same filter of course, R72.
And I know exactly what I am getting with IR every time I shoot because I work with it enough. Geir Jordahl did not publish a brilliant book with HIE in an Xpan by sheer luck, he had his system and down and anyone can with enough practice.