In the classic system (pre 2019, I think) there were two privacy controls -- people could opt out of receiving emails from other attendees and they could separately opt out of receiving emails from the event organizers.
I'd love to bring this back. It still gives the user the ability to opt out of getting emails from anybody, but it preserves the option to allow me to still communicate to them via email. Which is really necessary onsite if we have to make critical announcements -- sessions are starting late, room for a meeting has changed, etc. Not everybody has the app (where they'd see that as a push notice) or will log into the site on their phone, but everybody sees their email.