Because offending each other tends to make everyone angry and bitter. Being angry and bitter is generally not fun. Many online communities are joined with the intention to have fun, so it kind of defeats the point.
Of course, that's not always the point. I doubt anyone joined 4chan due to its reputation for being a "nice" place.
>Because offending each other tends to make everyone angry and bitter.
Not necessarily, you can get funny banter or a viewer-streamer interaction where all is made in good fun. The issue people are having is that twitch poorly understands or support this kind of nuance.
Alternatively: people have finally said enough to having their ability to use the internet gated on their willingness to accept abuse from other users.
Have you seen the response individuals get to calling out bullshit behavior? It takes guts to willingly put your name on any action to reduce the spread of abusive content. The people who do become victims of doxxing, swatting, unending abuse on all social media, including being sent porn, torture imagery, death threats, child pornography.
Then someone say that they're the snowflake? They're not the babies having a tantrum over not being able to call people intentionally abusive names.
Of course, that's not always the point. I doubt anyone joined 4chan due to its reputation for being a "nice" place.