There are lots and lots of reasons, but one advantage that comes to mind is that you're entirely in control of the data, you can just take your mail spool and l

There are lots and lots of reasons, but one advantage that comes to mind is that you're entirely in control of the data, you can just take your mail spool and leave for greener pastures whenever you want. You don't even need an export process, you already have all of the emails in your archive.