Uhm I'm not sure you really tried that out.
Once you upload an iWork file from a Mac to iCloud and open it with an iOS device, the file gets converted to the iOS version, the advanced features are removed from the file, and is reuploaded to iCloud. Just then, you can edit it on your iPhone.
I'm sorry you do not agree, but it's what's going on =P iOS version is simpler, and as long both type of documents can't have the same information, they can't be synced in real time like with Notes, Calendars, Reminders and etc...
Let's not forget, again, that Apple puts usability / ease of use first. If adding all desktop iWork features would imply a negative impact at the ease of use when editing a Numbers, in example, then they won't add it. And I think it's okay, iDevices are not for intensive work. Ergonomically speaking, they are not for intensive work. And will never be. They're best at what they are supposed to be, but not replacing a whole computer.
I'm an interfaces designer by the way, there is a lot of accessibility, use and other factors I keep in mind when writing this response, this is no deliberate answer in any way!
Cheers! =)