When watching the NASA channel (such as on YouTube) you see clouds and occasionally land forms. Why is it we never see electric storms on Earth ?
This footage shows a (sped up) view from the ISS passing over China, Korea and Japan with widespread lightning visible. Another beautiful example is this annotated image of Saudi Arabia and Kuwait taken from the ISS, showing city a lightning storm between the city lights:
Image Credit: NASA
Since lightning strikes occur 40-50 times per second over the surface of the Earth, if you watch the ISS livestream for long enough and the viewing conditions are good (ie. it's easier to see lightning on the night-side), you're bound to see some.