The main issue is of course not everyone reads their inbox, ever. Compounded by current inability (AFAIK) to stop stuff hitting it and instead just getting emailed, so it can get cluttered quickly, especially with a lot of subscriptions.

But that's a usability issue that I know's slowly being worked through, and frankyl if someone's email address is faulty then they ought to check their inbox when notifications fail. Perhaps a different category in the inbox for DW announcements and this sort of thing?