The biggest one for me is that, as I'm making a video, I get an idea for a joke that involves music but I can't use it as it may lead to a copyright strike (even if the bit is couple of seconds long). Also, as I'm making a video, I can easily get this melody that would be just perfect for the video, but yeah, again, copyright.
I mean, copyright's fine, it is just annoying that I have to find the alternatives in the Audio Library - there are amazing tunes in there, but it takes a bit of a searching.