Because right now more people are still using YouTube and it works well in posting Terry's video in a comment and it will not move you to another site unless you are using busy.org and watch a dTube video you will stay there.

If you share it in a Facebook question in what is Steemit it makes it easy to embed and play it there.

Until the time we get dTube and Dlive doing that it is best to cross platform post and use YouTube to place the messages and also upload it in dTube and Dlive eventually.