5 points
The issue not that you can’t export in bulk, you’re locked into their apps daily. Every other email provider out there uses standard protocols that allow for any client to be used.
Besides, the export feature is all fun until you actually have to use it. There’s a bunch of metadata that gets lost, contacts, calendars and notes are exported in JSON with propriety structures that other systems can’t deal with. Note that there’s also CardDAV/CalDAV as open and interoperable solutions for those issues and they device not to use them.