Personalised unsolicited email or any other type of contact can be an important way to make new connections, at least in my opinion.
If it's commercial and unsolicited, it's spam and I will treat it as such.
These aren't genuine requests. They're sending them to sites like mine where the request doesn't even make sense--the site isn't a blog, all they'd have to do is register and they could post any article themselves (I'd ban them immediately, but they could do it).
They're absolutely spam, and once you see a few of them you realize how formulaic they all are. There must be some tool that generates them, they usually just have some minor differences in words/phrasing (basically "spinning": https://en.wikipedia.org/wiki/Article_spinning).