My thoughts, given that I'm fairly new here on dev.to. It seems like make of the posts here are for sharing knowledge with the community so that they can learn, but also so that the developer can learn more by organizing their thoughts around it and engaging with the community.
Posts on a dev's own personal blog tend to feel more formal and polished, while much of what I see here seems to be a bit more informal, trying to organize one's own thoughts while also actively seeking feedback and improvement in this topic from a welcoming community.
And I think this is great; it's not just one person teaching the rest, or one person asking questions without trying hard to solve the problem. It's one person taking a good crack at a problem, sharing what they learned in the process, and also hoping to learn even more. So even if the content of the post itself might have been posted before, the discussions around that topic are always evolving, and for that reason we shouldn't strive to eliminate all duplicate content in the same way that SO does.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.