It's not as simple as you make it out to be, but you have me at a disadvantage as I've actually worked on products like these and can't rebut with specifics.<p>In the meantime, I'd dispute the idea that embedded developers even understand the relationship between secure random number generation and cryptography, outside of the abstract.<p>It's also the case that amongst security practioners in <i>general purpose code</i> there is still precious little best-practice understanding of how to groom and maintain secure RNGs; a Black Hat talk from just a few years ago busted up a bunch of RNGs on security products, both with algorithmic attacks and things like cold-start entropy.