Well, now I want to comment just so you upvote me! (Just Kidding)
I've never considered this before and I think I might start trying it (though I have a low SP at the moment and probably won't get much back). I still refuse to upvote begging or spam comments though...
It's just one of the ways to stack Steemit's rules in your favor.
If you don't have a lot of Steem Power, then getting lucky with a hot post by a popular author may be more valuable than upvoting all your comments.
However, another benefit of upvoting commenters is that you tend to rack up your follower count pretty quickly, and this can lead to greater profit on your posts.
I happen to be in a strange situation where I'm a low-end dolphin. Making $.05 per upvote makes a lot of sense for me, as long as I get a lot of comments that I can upvote. Hence my system.
I'll be honest, I'm not holding my breath that I will get anything back in terms of money. I'm just enjoying the community and relationship building. Steemit gives me a chance to hear voices from outside my regular social and professional circles and the relationship building has helped me to find a lot of interesting people!
A censorship-free social media platform will do that, yes.