Part of the issue with track and field in the US is that there is no organization at lower levels. Many time coaches won't talk to one another, nevermind share knowledge. Everyone is incredibly territorial, and as a result, there are different problems throughout because new ideas aren't exchanged. I see this at the college level getting athletes in the pole vault whose coaches haven't taught solid fundamentals.
And when you look at the relay teams, you see the same thing. Different college coaches teach different techniques for the handoffs, and after the trials the relay teams come together and the athletes haven't necessarily raced togehter before. 2 months ago I was watching Walter Dix run for FSU at the NCAAs, and now he's running for the US team. Not exactly a lot of time to work out the details. And the issue is further complicated by the use of different relay teams throughout prelims and finals. So the handoffs can be different throughout, with limited time to practice them.