1) Lack of client-side buffering. This is a benefit in real-time communication, but it limits your maximum bitrate to your maximum download speed. It’s also incredibly insensitive to network blips.

2) Extremely expensive. To keep bitrate down, video codecs only send key frames every so often. When a new client starts consuming a video stream they need to notify the sender that a new key frame is needed. For a video call, this is fine because the sender is already transcoding their stream so inserting a key frame isn’t a big deal. For a static video, needing to transcode the entire thing in real time with dynamic key frames is expensive and unnecessary.