YouTube has been the leading video and music streaming platform on the internet for some time now, and it doesn't look like anybody will be able to challenge those titles any time soon. Their revenue is derived mostly from advertising, but a paid option, called YouTube Red, rolled out about a year ago. For $10 per month, users got exclusive content, background playback, playback without video to save bandwidth in the YouTube Music app, exemption from YouTube ads, and free subscriptions to Google Play Music. The catch is, of course, that the Red-exclusive content mostly involves high-tier YouTube stars, and isn't a big selling point to most users. Ad-free playback won't be that big of a selling point to those okay with ads, of course, and background playback won't be that big of a deal to those whose handsets have decent battery life, who use Xposed modules for that purpose, or who actually watch music videos.
All of these factors combine to give YouTube Red pretty mediocre numbers. In the service's first year of life, it's managed to garner around 1.5 million paying users. While that number is fairly large for the four nations where YouTube Red is currently available, keep in mind that YouTube's user count numbers over one billion, with a huge amount of those being registered users that actively participate in the YouTube community. Essentially, it boils down to use cases and user perception; there are a good number of benefits to YouTube Red, but most users just see it as paying for something they've gotten for free for as long as they can remember.
Even with user growth as relatively slow as it is, YouTube seems happy with the state of things. The benefits to YouTube have been quite clear; creators who find themselves starring in YouTube Red originals find their view and subscriber count soaring, and YouTube Red subscribers tend to end up using YouTube as their main source of entertainment, often cord-cutting to favor YouTube. Between limited availability and issues with value perception, the fact that YouTube Red has managed to reach 1.5 million subscribers thus far may not be impressive, but it is at least healthy for now, according to YouTube.