You know, because ticking a single box to enable IMAP is hard. And because you wouldn't want to allow pretty much every device under the sun, rather than a few in the exclusive have-paid-microsoft/are-microsoft club to connect.
Enabling IMAP won't do a bit of good if it's not open through the firewall. Opening the hole in the firewall requires change control documentation for SOX purposes, good governance, and security sanity, and no change request gets approved without business justification. YMMV.
...though his invention worked superbly -- his theory was a crock of sewage from beginning to end. -- Vernor Vinge, "The Peace War"