Except of course for the big old 'Collaborate' button on Keynote's menu bar, where you can choose who should be able to edit or view the presentation - anyone with the link, or anyone you invited - mediated via iCloud.
To be fair it's a fairly recent addition - maybe in the last year or so.
> it was because they didn't understand the need for it
You keep making this claim but unless the person you knew was on the Keynote team I doubt they had any actual insight into the process.
There are a million things you could do. It is important to layout things in priority order. For example, unifying desktop and mobile implementations and file formats so when you do add collaboration features in the future the two can interoperate. Or adding a high-fidelity web experience so people who don't use your apps at all can collaborate. Perhaps those two things are important to get right before adding collaboration?
(Hypothetical, I don't have any knowledge of any of this).
To be fair it's a fairly recent addition - maybe in the last year or so.