Well, bobbba was correct, but just didn't word it entirely clearly:
iOS and OS X both support Microsoft Activesync. OS X even supports Active Directory. And they do license these technologies from Microsoft (and are happy to do it, and brag about it constantly in the enterprise; I know this because I used to give 'Mac in the Enterprise' presentations to local businesses on their behalf).
Thus, if you were to use an email service which supports Exchange Activesync, it would play perfectly well in iOS and in OS X. Case in point: my old university email, which they still provide to me for free (presumably in order to hit me up for donations/sell my address for spam), uses it. It syncs perfectly between its servers, its webmail, my Mac, my iPad, iPhone, and my Windows 7 and 8 VMs.
The issue isn't Exchange and Apple. It's Exchange and Hotmail, oddly enough. Perhaps originally to appease Blackberry users, and now partly to push the usefulness of WP7, Microsoft allows mobile users to interact with the Exchange servers for Hotmail. It does not, however, allow desktop clients access to those same protocols; instead, they create a special access channel for Outlook to incentivize using Outlook or webmail.
Anyway, in summary: this really, really isn't Apple's fault. It isn't Mountain Lion's fault, or Lion's fault, or any of that. It isn't that they're not compatible with the right protocols; it isn't that they haven't joined the right clubs, or done the right secret handshake. It's Microsoft deliberately making Hotmail worse for non-MS desktop users on purpose. And hey, it's a free email service; they can do what they like.
P.S. I'm not sure what the detection method is for blocking desktops from using the mobile Exchange servers, but it seems to work pretty freaking well; I've as yet been unable to find any way to circumvent it. Same goes for Gmail, which also uses Exchange for mobile-only (since they have easy syncing with Windows, OS X and Linux through other, open methods).