For a tl;dr:<p>While YouTube assures us that it's a very few number of channels which rely on community contributions, this paints a very blurry picture of how many users are reliant on these.<p>Not to mention use cases which aren't available to any of the alternative caption providers:<p>1) When a user uploads their captions or Google generates them, it’s often a one-time process. If there’s a mistake, no one is going to go back to fix it. But with community contributions, users can build off of previous work by correcting one another, not unlike how Wikipedia works.<p>2) Even though community contributions carry the risk of sabotage, they also provide viewers with the power to moderate. Someone snuck in a joke on a video you were watching? Just go into the caption editor and edit it out! Community Contributions spare channels of having to moderate these manually by relegating the task to channel viewers.<p>3) Where automated captions are stuck with plain text, and uploaders are limited by the time they’re willing to invest to stylize their captions, there are people out there waiting to tap into their potential. YouTube supports a plethora of caption/subtitle formats, which a seasoned captioner can use to add color, formatting and emphasis!<p>4) In translation, there are times when we don’t want it to be too precise. An example could be explaining the meaning of a word, the wordplay in a joke… And although there are techniques to recognize proper names, there are sentences that automated translation is not designed to handle.
For an illustrated version of this explanation see The Impact of YouTube Removing Community-Contributed Closed Captions