I think a huge majority blogging on WordPress.com have no interest in learning the tech stack to run something like Hugo. The quick start for Hugo includes command line git, which will probably make 99% of bloggers stop reading.
(n-gate.com seems to have died, but the prediction that WordPress.com bloggers would switch to static site generators and use git for version control would probably qualify as an example of the comical HN-bubble.)
The procedure can't get a lot less technical, and for some people this may be the right thing. Plus, since it's a SSG basically, there is not much to worry about vulnerabilities.
I tried it briefly and decided it's not for me (don't exactly remember which drawbacks killed it for me), but I think the approach has some value to it in general.