I think their main focus is allowing people to code who only have a mobile phone, so my guess is iPad is a lower priority (because most people with iPads have full size computers they can use instead).
iPad users also have access to the desktop version of their site
Making it scale properly to iPad screen sizes and doing nothing else shouldn't be too hard to do and would make it a lot more useful for people. Even if they don't want to spend the time developing an iPad specific layout, no reason not to use the full iPad screen with the current layout.