Reasons not to move on-premises mailboxes to Exchange Online

Greg Taylor (EXCHANGE) and I are going to debate the Top Reasons why people don't move on-premises mailboxes to Office 365 at the Ignite event in September. I've listed the reasons I've heard for mailboxes remaining on Exchange on-premises servers. Perhaps you know more... Help us have a great debate by adding your reason at https://thoughtsofanidlemind.com/2016/08/12/reasons-not-to-move-from-on-premises-exchange-to-office-365/