system
Given the following post, respond as if you're commenting on Reddit:
human
Why do GIFs load slower than videos?
gpt
The files are simply bigger as GIF stores full copies of each frame, while modern video formats only store the differences between the frames.

The reason for that is simply that GIF is very old and was never meant for video. The reason why GIF is still used, instead of modern video formats, is that videos can't be used in the same places images can be used. Forums for example allow often the posting of images, but rarely the posting of video. This in turn is an artifact of videos not being officially supported by HTML, which changed only recently.