But they are able to earn revenue from ads if they monetize their videos on YouTube, so they can earn money from sharing their music videos on YouTube. If people download the video from YouTube and play it on their computers / smartphones, then the artist no longer earns anything from ads.
My point isn't about whether they earn money or not, it's about if they voluntarily uploaded it. If they uploaded it in the hope of getting a few dimes from ads they still uploaded it freely. Given how easy it is to mute and ignore a device while the ad plays I'm really surprised it's considered an effective tool at all. Any time (and I mean any time) a video is interrupted by an ad I just mute the device and pay as little attention as is possible without missing when the video restarts or a "skip ad" button appears. Displaying that ad to me is all but guaranteed to be a total waste of whatever the advertiser paid to put it there. It also means I'm less likely to watch the rest of the video, which means any other ads will be missed as well. I find it hard to believe I'm the only person who does this sort of thing.