Because here I own my ID and I don't have to worry (so much) about being censored or shadowbanned. Also because I am not tied to one single client.

In many ways (in the ones that matter the most) it simply is a much better UX than Twitter was these past few years, and it takes me back to the mid 90's when I was using IRC which for me was when "social media" actually peaked (so, it peaked before it officially existed really).