Back in "the day", users were bombarded with warnings to never give out their email address, lest something bad happen... at one point in time, if you did post your email publicly, it would quickly become unusable as the spam tools & regulations were way behind the spammers. I'm sure there's still a huge contingent out there afraid of putting their email into the wild.

Perception is far more important than reality.

When online sales first took off, credit card theft was a huge concern. Even though nothing would go wrong for the vast majority of people fear was enough to make users and vendors go to great lengths to protect data. Not a perfect analogy but conceptually similar.