>>4941Because it prevents creativity. Take this GIF for example. If you hadn't seen it before and only glimpsed it at the very end of its play, the whole point of the person posting it is nullified. Autoplay also means you then can't do thumbnail fakes either.
Sure, your stupid reaction images wouldn't see any change, but for people who actually want to be creative, you're robbing them of being able to do interesting things.