This feature is part of the YouTube Red subscription. Which doesn't really add that much in addition, aside from partial ad removal and video downloads, all completely free on PC.
I could also invest those monthly bucks in some Patreon subscriptions to my favorite channels, which gets them drastically more and makes them less dependent on YouTube. It would even let me set the precise amount and distribution. And not pay a shady ad company on top.
I'm doing my part to shill the free (but sideloaded) Youtube Vanced app for Android - sadly not available for iPhones.
Gives you all the features of YouTube Red - including the ones that were available BEFORE Google silently removed them to put them behind a paywall, like background play!
Also includes experimental features to use crowdsourced data on where ads are in videos and automatically skips them if desired.
For some people, this is quite valuable.
As a side note, the video downloading is made available in the mobile app as well.