The most popular way to defeat email based user privacy services (as provided by Apple, Firefox, etc.) is to require a phone number for "verification" or "security" purposes.
In addition to being harder to acquire in bulk, phone numbers serve as a convenient non-anonymous and universal user identification key that can be easily matched by data brokers and shared to track customers across multiple businesses.
Facebook pioneered this approach by adopting SMS-based 2FA as a means of acquiring phone numbers to match users with purchases at partner businesses.
Phone numbers also enable businesses to send unsolicited text messages and robocalls.
In addition to being harder to acquire in bulk, phone numbers serve as a convenient non-anonymous and universal user identification key that can be easily matched by data brokers and shared to track customers across multiple businesses.
Facebook pioneered this approach by adopting SMS-based 2FA as a means of acquiring phone numbers to match users with purchases at partner businesses.
Phone numbers also enable businesses to send unsolicited text messages and robocalls.