Cameras write files with extremely short GOPs and overly high bitrates because they have to capture live video and can't know what the next second of content will look like. They need to use settings such that pretty much anything captured by the lens will be captured in good quality.

An offline encoded h.264 video can have far more processing thrown at it. Typically you'll see longer GOPs and a much tighter tuning of bitrates and more features like b-frames and CABAC encoding enabled.

A file directly off a camera can have bitrates of several tens of megabits a second. Even short videos are huge and won't stream well to many. A lot of devices also have limits on the profiles of video they'll even decode.

Someone throwing a camera's direct output onto YouTube can be guaranteed better than 99% of all devices on the Internet can be served a watchable version of the content.