I think some of the benefits that come from having your own space on the internet can also be achieved other ways. For example, maybe you've got a Github profile with some fun projects or forks. Maybe you just like hawking neat code snippets on Twitter or elsewhere.
So, I don't think writing is required - but I also think it can be very beneficial and we can't deny that.
Ah that makes sense. When I read blog my mind goes immediately to personal blogs which to me it means a space where you write about everything that interests you, not some some specific topic. But you're right, if one doesn't care about that they can achieve the same with some more specific and more focused platform (for example GitHub as you mentioned)
So, I don't think writing is required - but I also think it can be very beneficial and we can't deny that.