Just curious, how do you know that? I would have thought many establishments would have moved on by now. That said, I've a few of my personal programs that still run on IV - no need to change them as they still work fine (but then they're not running under the auspices of some institution where updating has relevance).
I suppose a more relevant question would be what is the breakdown type of institution still using 77 - educational, research, government, commercial etc. (I know airline bookings and traffic systems used a lot of 77 until recently). I note from another poster CERN is using 95.
I'd reckon legacy systems would be more likely to be found in govt. and commercial and updated more likely in research. (I'd expect there'd be a large disparity between the different types of institutions.)