This functionality isn't included in the newer phones because people aren't demanding it. I personally have no use for it, my personal email is Gmail and my work email is Exchange. In fact the move away from USB sync is a giant leap forward in my opinion.

I guess if you still had a pure POP3/SMTP mail solution that required you to download all your email to a local client such as Outlook, the USB sync would be of benefit. But doing email that way is antiquated. Use IMAP instead of POP3 and then your need for USB sync goes away.