Debug assertions in game binaries for blizzard and blizzard-branched studios are more common than you might expect. At least at ArenaNet, it was studio philosophy to ship with most debug assertions enabled so we could gather crash reports in the field to fix bugs. We only exempted assertions where the checks would cause performance issues (i.e. in a renderer or audio mixer). Most of our engineering culture was inherited from Blizzard and I think that particular rule was too.