I don't believe they are spammers or farmers, because those people usually create two spammy hubs and then follow 500 people.
I recently hit the follow button on a hubless author because he leaves great comments around Hubpages. He makes no excuse for his lack of hub writing, and he is just here to enjoy the other aspects of Hubpages, therefore, in my eyes, he contributes something of value to the community.
I think it's sort of like being a book author and most of your readers are not writers, which is how an author makes money.
Hubpages is first and foremost a writing platform, but all the things we can get involved in here helps to promote our writing, so I'm happy to get to know non-writers.