MP4 videos are not usable at least at this time. Sometime in the future maybe but right now that is the case, so that is why.
If you have read Admin's post here you know that they are taking action on all of the problems.
http://forum.mtu.com/showpost.php?p=78756&postcount=14
Bill Gates and Microsoft have made sure that nothing involving a computer is simple and easy anymore. Personally I have in all my years not seen anyone be able to release a perfect program that could run on any computer with any configuration. If we all had computers cloned from one perfectly set up computer then they would all work error free, or so you would think. I have worked for the government where they tried to do that and it doesn't work.
I could say it is a learning experience but that would be tacky. However in todays world of computers you have to know something about the computer or have someone you can ask (forums, friends, etc.) to be able to run one without having major problems. If you want simple and easy use WinAmp with their Karaoke Plug-in. If you want a Professional Karaoke Show use Hoster. Yes right now there are still some bugs in the new set-up but MTU is working hard and long hours to get those worked out to give us the best product. But even the best bug-free program is still going to require that you know or have a source of information on how to keep your computer up-to-date and functioning correctly.