Many of the CHM's videos already were on its own site, but they partnered with YouTube because of bandwidth issues. An important side effect is that YouTube can bring scores of new viewers who otherwise wouldn't seek out the CHM resources.
Nothing beats visiting the CHM in person. I've been there four times and there are always new and exciting exhibits, particularly in the "visible storage" warehouse and in system restoration rooms. But I live on the east coast, so attending their lectures is impossible. Video is the next-best option.