While blogging is an ancient concept, it is still one that (like emails) sticks with many (humans and systems alike).
For some it is a strategy for SEO and traffic, for some it is revenue.
The key to successful blogging is consistent output (which I lack sometimes), a subject that matters, and a language that is easy to digest.
Pros — SEO, thought leadership, knowledge transfer, showing off
Cons — time-consuming, writing is not for everyone, showing off
With many platforms having blogs by default (thanks WordPress for pioneering back in the stone age) it is easier than ever to start.