Why does High-Sec Exist?

So which is it?

Are these “trade hubs” designated by player action (as volume of trade) to which CCP then confers special “trade hub” status, or are they immutable arbitrarily designated by CCP?

What is the threshold of player activity for designation as “trade hub” by CCP?

What was the designated Caldari “trade hub” before Jita?
Was it always Jita?
Was there even one?

Why was Yulai not conferred designated “trade hub” status?
Its a CONCORD Assembly system, not Empire strictly.
I also just read CCP removed gates from Yulai?
Why did they do that?

Was Jita itself not just a agent hub, before it became a designated “trade hub” and had its agents removed?

What about Minnie space.
Are both Rens and Hek designated “trade hubs”?
If so, why are there two so near each other, when other Empires only have one?