@Elliandre, If you download something made with CC, it won't be present in what you downloaded unless you have the CC yourself. So if someone uses a CC hair that you don't have, the sim will be bald. CC itself is not included with gallery downloads.
That's why, even though I use a lot of CC, I avoid anything on the gallery made with it. First, because I like to choose what CC I want myself, so I'm not going to "go get it" just for a gallery download, and then 2nd, because it makes for bald, naked sims, or missing furniture, etc. on lots.