There's a lot of "I type fast on qwerty so why would I bother switching?" Speed isn't even the main reason I use dvorak. The primary reason is that it's more comfortable to type in.

In addition, as a programmer, a lot of the characters actually happen to be in more useful positions than in qwerty, even though that's not what the keyboard was designed for. '-_' especially is in a better place (home row, right pinky). Brackets are next to parens. '=' is slightly more convenient. Even in VI I find I like a lot of the key positions better.