Joseph, the only way I know of to "encourage" readers to comment, share, vote up, etc., is to churn out content they can't resist. It certainly doesn't help to "suggest, plead, cajole, threaten or beg"--not that I'm saying you do any of those things, but the only time the "average" reader will give you a Vote Up is if reading a page of your work leaves that individual thinking,
"Wow! That was really GREAT! I wish I had written THAT! This guy's a freaking GENIUS!"
Okay, so that's a slight exaggeration, but...well, here, think about it this way:
There are certain writers here on HubPages that I KNOW I'm going to Vote Up before I even read their Hubs. WillStarr, for example, the absolute master of the short story twist ending. Or if I'm in the mood for pure, unadulterated INFORMATION, Patti Inglish. In the political sphere, from the conservative viewpoint, TheFrogPrince never misses the mark.
These (and numerous others) produce consistently engaging material.
Bottom line, it's not up to the readers to be "very engaging". It's up to the writer to produce engaging material.