Decision to peer-review a paper by author who does not believe in acknowledging reviewers
In my opinion, you are overthinking this.

Academics do many things as part of their jobs, some highly visible, some behind the scenes; some acknowledged, some not.

In addition, social norms vary by discipline, by geography, and by individual. I have thus far once acknowledged a reviewer, since their comments improved a paper of mine signficantly, more so than others with whom I workshopped it with previously. However, I certainly don't write such acknowledgements as a matter of routine. To me it would feel like meaningless boilerplate. 

And frankly, while I do appreciate the importance of the peer review process, fairly often the nuggets of gold are also mixed with piles of dirt -- reviewer comments which, while well-intentioned, are at best of marginal value and yet take lots of time to figure out how and whether to address for at best slight benefit. I think most authors feel this at various times, and so while we recognize the worth of the peer review process overall, and if we are honest also recognize it has on balance improved our paper, our mindframe may not be exactly condusive to writing effusive acknowledgements once we finally craft a reply to comment #17! And it's good to recognize this mindframe challenge when we are playing the reviewer role as well.

Finally, I view the activity of reviewing more as part of my membership dues to my profession, not as anonymous acts of kindness to authors. I feel positive when sometimes (and I don't go out of my way to check) my reviewer's contributions get reflected in the final published paper, but I'm not sure I would notice whether there is a pro forma acknowledgement at the bottom or not.

However, this is a worthwhile discussion to have. I will henceforth set the bar under which I as author acknowledge in this instance lower, since your question has brought to my attention that you, and presumably other people, care about this more than I do!