Honestly, one of the big problems is that people confuse crypto primitives with crypto schemes. Developers need schemes, not primitives. Some people, who know what they're doing, need the primitives, but they are by far and away the exception.

AES is a crypto primitive, AES-CTR-CBCMAC (aka, AES-CCM, but spelled out to emphasize the complexity of it) is a scheme. And even then you have key distribution problems, which is essentially clipping on another two or three car batteries.