iPad's announcement caused many people to wonder why Apple decided to use an ancient standard for video output rather than a more modern protocol, such as DisplayPort or HDMI output.
About ten years ago Apple changed Macs output from VGA to DVI standard that supported HD resolution displays and improved digital accuracy. Few years later Apple made another shift – from DVI to DisplayPort. So why Apple chose VGA output on the iPad? There are 2 main reasons:
Most of the video projectors support the iPad’s resolution of 1024x768 over a VGA port.
VGA is sufficient to handle the iPad’s resolution, and it is really cheaper and easier.
For more details – watch the video of Daniel Eran Dilger from the RoughDrafted Magazine: