Still nowadays? My impression is that in (pure) math it's lost most of its market share in the last few years. But maybe that's only in my circles.
Of course there is a whole constellation of more specialized things in certain fields, that has come a long way in the last 15 years. So people needing things like that no longer kludge things together in Mathematica.
https://www.12000.org/my_notes/CAS_integration_tests/reports...