It's rendered by your browser so you get properly subpixel-hinted text instead of the horrible, blurry, compressed screenshot effect a video or gif gives. Also

It's rendered by your browser so you get properly subpixel-hinted text instead of the horrible, blurry, compressed screenshot effect a video or gif gives. Also it's more convenient to generate than faffing around with screencasting software. Edit: well, not (lossily) compressed in the case of a gif but not as nice as text properly rendered for your display.