1) People want to post Youtube videos that jump to a specific time in the video. The following URL should jump to 1 minute 30 seconds, but Xenforo ignores the time stamp and it starts from the beginning.
2) Some users want to post a lot of videos in their thread and embedding causes it to load up very slowly. They would prefer to post all the videos as links rather than embedding.
3) Occasionally some users want to post the link rather than embed the video. Really a personal preference.
Ideally, there could be a checkbox at the end of the post that states "Auto Embed Media". Default could be checked but the user would have the option of unchecking it so that any media links are not embedded.