It seems to have become a taboo topic. There are too many people who voted for it and now realise it has been a mistake and want to forget about it, anyone who reminds them, will be seen negatively. It also can't be reversed anyway so there's no upside in this discussion - reversing means becoming "just one" of the EU states because the Union has been explicit that they won't allow any perks, not even keeping the pound - which is just too much for public to stomach.