The issue is that uploading full movies online can and will affect sales of that product. People will go "Why buy the movie when I can watch it online for free?" While some people may buy the DVD to get better quality, likely, in my opinion, most people will just watch the movie online and not pay, thus hurting Universal's profit. And money is needed to make more movies. If a movie makes enough money, it may earn a sequel, like LBT has in the past many times. But uploading full movies will not help LBT. Instead, it will hurt it. While some may still buy the movies, many may not, since they can watch it for free. This takes away money from Universal's profit, and as a result decreases LBT's sales. Uploading full movies may seem to be a good way to promote the product, but in the end, it causes more damage than good. There are other ways to promote LBT without hurting its sales. Fanart and fanfiction are a couple of them.
Keep in mind I am talking about full movies only; music videos or clips likely aren't going to cause as much damage as a full movie would.