"Why did Apple end iDisk at the same time that they rolled out iCloud?" That's a good question.
Apple didn't end iDisk when they rolled out iCloud. They did announce they were ending iDisk.
Apple is ending iDisk because they don't want to be in the businees of hosting users data, or web spaces either. I don't see why anyone should be upset or care about it, they can go elsewhere for those services with companies that want to be in that business.
iCloud is not a data hosting facility for users. It is a service that allows user of Macs, PCs, iPhones, and iPads to sync their current mail, calendar, contacts, photos and iwork docs.
iCloud is not a Photo repository for the users. It collects the current photos off you devices and streams them to you other devices. After a month they disappear from the iCloud stream. In that time you should have pulled and save the photos you want on your other devices.