Interesting - I never thought of the Thinkpad niche as developers, I thought of it as business professionals. In an airport, it used to be the way you knew someone worked for a consulting firm was that they had a Thinkpad, especially if it was a tablet.

That might explain some of the keyboard choices. Caps lock, function keys, and the insert key might have important uses for developers. But if you're creating business documents, caps lock is unnecessary, insert confuses you when all your text starts getting over-written, and the function keys don't really do anything.