Why didn't the difficulty adjust for the first 30,240 blocks? I'm working on showing the difficulty adjustments over time, and I've noticed that the first difficulty adjustment did not take place until block 32,256:

http://learnmeabitcoin.com/explorer/node/difficulty/

Why is this?
Because blocks were not being mined in less than 10 minutes on average during this time (so the difficulty would only decrease and not increase), and the difficulty cannot go lower than 1.