The proposed bulleted list has its merits, BUT I think that AWS' current selling line (about lower TCO) is quite good at gathering support from those that might (still) judge things in the traditional terms of ROI. SO, the choice might be deliberate?

Amazon is about cost, they understand cost and want to remain "trusted" about cost. The others benefits you list are bonuses to the central argument that Amazon wants to deliver services to you at the lowest possible cost.