reaction vids are a nice way to see how the community is responding to an anime, tv show, or youtube clip. It's essentially like harassing all the people you know to watch something you're interested in that they don't give af about, except reactors do it willingly. For money passion.
When you think about it's not too much different than watching First Take or Undisputed to see how they react to the previous nights games (because they rarely do deep analysis on there, it's mainly hot takes if we're being honest), and I'm not gonna lie there's some stuff I never would have watched by myself (judge shows, romance shows) that I only watched because someone was roasting the hell out of it on YouTube. For example, they had some show where this simp fell in love with an inmate that reactors were flaming.
You can question if some of them are really earning the money they're making (I mean some are racking in hundreds of thousands a year on Patreon, not even counting the YouTube ads, just to essentially watch tv and youtube), and they usually hire an editor to make the video. Soo...a lot of them really aren't even doing anything, but ultimately unless legislation changes they will continue to fill the market, and the more technology separates us and the less we go outside to make in-person friends the larger the market will grow and the more money they'll make.
In the future, I even see some small time shows paying reactors to watch and advertise it. It already happens for music, Imdontai said companies were offering him 10k to review music on stream. If you're at all interested in this, the time to start is probably now.
side note: completely unrelated anyone interested in making a group anime reaction channel ?