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True, although you'd need longer distance to subject to get the same compostion; not sure there's a net win here.
Anyhow, when you start getting into such specific cases of individual situtions where a 70/2.4 doens't cut it, all that does for me is emphasize just how many other situations it *does* work well for. And it also gets me thinking about how else I could cover those situations where the 70/2.4 doesn't cut it. Eg, head & torse with really shallow DOF: no reason a $25 M50/1.7 couldn't cover that. Or if you want something longer on occasion, a $100 M100/2.8, $200 M85/2, or a more expensive 90-100mm macro if you can't live without AF.
I guess if I thought an 85/1.8 were just so perfect that it would eliminate the need for any other portrait lens, that would be one thing, but it wouldn't really be that for me, and I don't even do portraits. So given that it pretty much still leaves you wanting something shorter, as well as sometimes something longer, and most people wouldn't realistically wouldn't be using it wider than f/2.4 "most" of the time for portraits anyhow, it just doesn't strike me as that great a loss; either way you nedd two or three lenses to get the job done.
Not that it wouldn't a nice option to have an AF85/1.8 be available as one option, though. But I can totally see why there is more call for the cheap fast normal.