Because plenty of secondary sources have covered it.

Wikipedia's philosophy is that it summarizes reliable secondary sources. You're asking for Wikipedia to change its fundamental philosophy so that editors go out and gather primary evidence themselves, debate it, and then deduce what's true by themselves. That would work if Wikipedia were edited by a select group of highly qualified people you can trust, but it's not. It's edited by literally anyone who signs up. So the rules are strict: find a secondary source, or else don't include the info.