I consistently hear people on YouTube complain that the subscribe button doesn’t do anything for viewers, now that channel notifications are controlled by the bell. But it does do something: it puts the videos from that channel in your subscription feed, which is readily accessible on all versions of YouTube. So why do people act like it doesn’t exist? I think it’s super convenient, especially if you’re subscribed to a ton of channels and don’t want your notifications feed flooded with new videos.
I believe it’s because a lot of people (or, enough people that it’s a thing) will subscribe to a channel for a specific sort of content, not a personality. If the channel starts to do things that aren’t that content, then people will unsubscribe so as to avoid seeing random things they don’t want to have cluttering up their subscription feed.