updated 04:11 pm EDT, Wed October 9, 2013
No reason given
AOL is dropping iCloud support from its Alto webmail client, according to a notice being sent out to users. Alto is a multiplatform service, allowing people to check mail for AOL, Gmail, Yahoo, and custom providers. As of December 2nd, however, Alto users with an @icloud, @me, or @mac address will no longer be able to check associated messages there.
No explanation for the cutoff has been offered. One possibility is that AOL simply isn't seeing a enough iCloud users to justify special support for the platform. Those people may be more likely to check messages through Apple's Mail apps for OS X and iOS, or iCloud.com.