To play a devil's advocate, I want to answer this directly as answered. Available information indicates that NSA used various coercion tactics to ensure cooper

To play a devil's advocate, I want to answer this directly as answered. Available information indicates that NSA used various coercion tactics to ensure cooperation from various companies and that it has the methods to ensure hardware modifications in its own interests. So the damage to NSA from improving security too much is less than damage to my ability to use the computing device I have paid for as an actual computing device. Of course we should also consider smaller threats. But the better the platform is locked down, the less limitations there ae for advertiser-friendly platform design, which makes people expect a lot of permissions requested by applications, so phishing and trojans become easier. The problem here is about the effects of scale: it is hard to produce just a few thousands phones with good specs.