The benefit is that their post will be more likely to receive upvotes and resteems, etc.
Example. I just resteemed a post. I see your standard comment on my post, but there's a little section that states the following:
_Users are encouraged (but not required) to upvote, resteem, or comment at least two other posts on the @resteembot blog. We help ourselves through helping others. Good luck. _
It sounds reasonable to me, so I click your name, upvote a post, resteem another, and I'm done. Maybe I see something that interests me. In my case I learned something about money laundering and that there are contests on steemit for photos of fruit and vegetables.
I like it!
Not only will it create perks for using the bot, but it will also keep the feed clean of spam (since the same users can downvote that spam).
Still - I am not as optimistic as you that others will see this initiative as benefit to them. Also - those who do will eventually get tired.
But if I keep reminding people that the content is cool, some will always check it out. Even if it's just 5%, that's still something nice.
But I am thinking of doing something cooler. In each comment I'll include the link and name of the previously resteemed comment.
Something like "I just resteemed you, but did you know that \user\ wrote \title\ and got it resteemed right before you? Check it out, as well as the other stuff in my feed"
I like that too. The only thing is that it only exposes the post to a single person.
Regarding users not seeing the benefit, if enough do it, people will notice that they get more upvotes when they use the bot. As their posts trend, more people will see the comments at the bottom of their thread and use the service.
I thought of something else, but you would have to give some kind of reward. If you made a hashtag like #resteembotsentme, then it would let people know their investment worked. It would also be good advertising because they would see your comment there ad well. But you would probably have to add an incentive.
The next person sees the same thing, reads my post and likes it, upvotes it and resteems it. Your service just became that much more valuable.