Copyright infringement issues, a majority of artists and producers don’t allow their music to be used freely and you need to acquire permissions and likely pay money to use them. Most publishing sites like YouTube scan the videos as they are uploaded and search the audio for infringements.If any are found they disable the audio in the video. So to actually put whatever you want music wise into one, you need to go through a more private host.Most likely you will hardly get views because they are off putting sites that people don’t recognize. At that point it’s hardly worth the effort of making a video.