I haven't seen this personally on any of my hubs, but I know sometimes it is hard to know what to say. Sometimes it takes longer to leave a reply than it does to read the hub itself.
About the only time I have felt that someone was just making an appearance was a gal (I won't say her name), but the only comment she ever made was "Great hub". She has not stopped by to visit me yet, but hopefully she would be willing to invest slightly more than that.
Perhaps it's just me, but I like to engage. And, to be quite honest, I am not a big fan of people "following" without giving a reason for doing so. To date, I do not believe I have ever followed anyone, without telling them why I have done so.