It is too soon to talk about 6th reason, because the candence is slow, lots of titles haven't published yet, and the plans for the brand are multimedia. This means they are going to worry more about movies, teleserie and videogames what the printed books.
The experencie has tought them the best way to get new players is with simple rules.
Maybe the plans for a future d20 system is to be simple, but enough modular and flexible to allow different genres, even space opera and superheroes, but with a right balance of power.
But I dare to suggest they are going to get the idea from Pathfinder 2 where some racial traits can be replaced by optional racial feats.